US2860275A - Indirectly heated cathode - Google Patents

Indirectly heated cathode Download PDF

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Publication number
US2860275A
US2860275A US562341A US56234156A US2860275A US 2860275 A US2860275 A US 2860275A US 562341 A US562341 A US 562341A US 56234156 A US56234156 A US 56234156A US 2860275 A US2860275 A US 2860275A
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US
United States
Prior art keywords
cathode
sleeve
particles
indirectly heated
insulating material
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
US562341A
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English (en)
Inventor
Duran Johannes Christiaan
Dams Jozephus Franciscus
Moubis Gerard Charles An Marie
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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 US Philips Corp filed Critical US Philips Corp
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Publication of US2860275A publication Critical patent/US2860275A/en
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    • 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
    • H01J1/24—Insulating layer or body located between heater and emissive material

Definitions

  • the invention relates to indirectly heated cathodes for use in electric discharge tubes, and more particularly to cathodes of this kind in which the space between the heater element and the cathode sleeve is filled by sintered insulating material.
  • the thermal conductivity is reduced by such cavities, and since the cavities will be formed at different points in difierent cathodes, cathodes having difien ent operating temperatures will result, which non-uniformity is undesirable. Further, the heater may become overheated locally so that the heater filament becomes brittle.
  • This method provides the advantage of ensuring a partial separation between the finer and coarser particles of the suspension, particularly if the height of fall, i. e., the distance the particles have to travel, is chosen sufficiently large.
  • the coarser particles become located substantially at the. bottom and the finer particles substantially at the top.
  • the greater part of the coarser particles become consequently located in the proximity of the closed end while the greater part of the finer particles become located in the proximity of the open end.
  • the coarser particles are only slightly sintered and consequently shrink slightly only, while the finer particles subsequent to sintering exhibit a great mechanical strength and satisfactorily seal the open end.
  • the coarser particles produce a porous mass having some resiliency so that the formation of shrink-cavities is avoided.
  • a height of fall of from 2 to 3 times the length of the space to be filled has proved advantageous particularly 2,860,275 Patented Nov. 11, 1958 when sedimentation is accelerated by the use of a centrifuge.
  • FIG. 1 shows a holder for the cathode sleeve and the suspension during sedimentation
  • hFig. 2 shows a centrifuge provided with such holders
  • w ile Fig. 3 is a sectional view of a cathode of the invention after sedimentation and sintering.
  • reference numeral 1 denotes: the emissive part of the cathode, in the case shown a dispenser cathode of the type described in U. S. Patents 2,543,728, 2,700,118 and 2,700,000, reference numeral 2 the cathode sleeve or support in which the emissive part 1 is secured and supported, and 3 the heater arranged in the cathode sleeve 2.
  • the cathode sleeve 2 has a ridge 4 formed in its periphery.
  • the assembly comprising the cathode 1, the sleeve 2 and the heater 3 is introduced into a metal holder 5 until the ridge 4 engages with the rim of the holder 5.v
  • Said holder 5 has a cavity 9 formed in it which is provided with a tapered part which registers with a second cavity within which the cathode sleeve fits.
  • the holder 5 is arranged together with the cathode assembly in an aperture 7 of a second holder 6 which may, for example, be made of synthetic resin.
  • the cavity 7 has a recess 8 in its bottom in which the cathode 1 is accommodated.
  • the space 9 is now filled with the suspension of the insulating material to be introduced into the cathode sleeve.
  • the size of the particles is preferably from 1 to 15 microns.
  • the height of the space 9 is at least equal to the length of the cathode sleeve 2.
  • the coarser particles of the suspension settle first and consequently come to rest substantially at the bottom in the proximity of the closed end of the cathode sleeve, the mean size of the particles decreasing in the direction from bottom to top.
  • the liquid is decanted or evaporated and the holder 5 is taken from the holder 6 and heated until sintering of the insulating material occurs.
  • the filling of the cathode sleeve consists substantially of coarser particles 12 (from 10 to 15 microns) while the percentage of finer particles 13 (approximately 1 micron) gradually increases towards the open end.
  • the sedimentation can be considerably accelerated by the use of a centrifuge, as is shown in Fig. 2.
  • the holder 6 can be suspended from an annular member 11 which is supported from arms 10 of a centrifuge. With a height of fall of from 2 to 3 times the length of the cathode, substantially complete sedimentation is produced after a period of from 5 to 10 minutes at a speed of 3000 revolutions per minute and with a distance between the cathodes and the axis of approximately 10 to 15 cms., the solid substance filling the cathode envelope to the level shown by a broken line 14 in Fig. l.
  • the sintering of the A1 0 is eifected by heating for two hours at 1000 C. and subsequently for 15 minutes at 1600 C. It was found that no cavities are formed either during filling or during sintering. It is necessary that the suspension contains particles of different sizes so that preferably ground insulating material is to be used as the initial material.
  • cathode Although one embodiment of a cathode has been described, that is to say a so-called dispenser cathode, the invention can also be used with tubular cathodes.
  • An indirectly-heated cathode comprising a sleeve member and a heater within said sleeve, and pulverulent in and closing ofi one end of said hollow support member, 10
  • a heater element within said hollow support member, and a sintered' mass of pulverulent insulating material filling the space within the hollow support member and surrounding the heater element, the portion of said insulating mass adjacent the electron-emitting member compri's- 15 4 ing mainly coarser particles, the portion of said insulating mass adjacent the other end of said hollow support member comprising mainly finer particles.

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  • Electrolytic Production Of Metals (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US562341A 1955-02-09 1956-01-30 Indirectly heated cathode Expired - Lifetime US2860275A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL785177X 1955-02-09

Publications (1)

Publication Number Publication Date
US2860275A true US2860275A (en) 1958-11-11

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ID=19832255

Family Applications (1)

Application Number Title Priority Date Filing Date
US562341A Expired - Lifetime US2860275A (en) 1955-02-09 1956-01-30 Indirectly heated cathode

Country Status (6)

Country Link
US (1) US2860275A (fr)
BE (1) BE545031A (fr)
DE (1) DE1009315B (fr)
FR (1) FR1140831A (fr)
GB (1) GB785177A (fr)
NL (1) NL100082C (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB381551A (en) * 1930-06-17 1932-09-29 Gira Soc Improvements in or relating to the manufacture of moulded materials
US2647216A (en) * 1950-04-01 1953-07-28 Rca Corp Dispenser cathode

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB381551A (en) * 1930-06-17 1932-09-29 Gira Soc Improvements in or relating to the manufacture of moulded materials
US2647216A (en) * 1950-04-01 1953-07-28 Rca Corp Dispenser cathode

Also Published As

Publication number Publication date
GB785177A (en) 1957-10-23
BE545031A (fr)
DE1009315B (de) 1957-05-29
FR1140831A (fr) 1957-08-14
NL100082C (fr)

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