US2593856A - Electric discharge tube of the kind comprising an indirectly heated cathode - Google Patents

Description

April 22, 1952 H. J. DE WEYER ELECTRIC DISCHARGE TUBE OF THE KIND COMPRISING AN INDIRECTLY HEATED CATHODE Filed Feb. 17, 1949 J /1/ /l nl//ll/1/A/4/4 /l/A /l/ /f /v////////// I//// /l fA 41m/EMM.

HENRICUS JOHAQINES DE WEYER 4 .U BY w 7AGENT Patented Apr. 22, 1952 l ELECTRIC DISCHARGE TUBE 0F THE KIND -ooMPRIs1NG AN INDIRECTLY HEATED ,oA'rHoDE Henricus Johannes de Weyer, Eindhoven, Netherlands, assignorto Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application February 17, 1949, SerialNo. 76,884 In the Netherlands March 15, 1948 4 Claims. (CL 313-331) The invention relates Vto an electric discharge tube having a cathode of the indirectly heated type comprising a cylindrical sheath in which one or more heating wires are housed and in which the space between the sheath and the heating wires, at least adjacent the ends of the cathode, is fully lled with insulating material.

It hasbeen found that the ends of the heating wires which emerge from the insulating material at the ends of the cathode frequently break off at thearea where the said heating wires emerge from the insulating material, on being bent to connect them to the supply conductors. Since we are always here concerned with comparatively thin heating wires which by themselves may-be readily bent, this phenomenon could not be foreseen The phenomenon is particularly inconvenient withcathodes of the indirectly heated type produced by mechanical operation, such as swaging,

rolling and drawing of a complex conductor, the. space between the conductors being consequently filled with strongly compressed pulverulent insulating material. Although the heating wires for such cathodes may be very thin, so that bending thereof should prove to present no diiculty, the said phenomenon is found to occur to an even marked extent.

The diiliculty may be obviated, if, in accordance with the invention, with an electric discharge tube comprising a cathode, of the indirectly heated type which comprises a cylindrical sheath in which one or more heating wires are provided and in which the space between sheath and heating wires, at least adjacent the ends of the cathode, is completely lled with insulating material, 5

the ends of the heating wires'which ends protrude from the insulating material, are iiattened, at least in part, starting at a slight distance from the point at which these ends protrude from the insulating material.

The flattened part as distinct from the remaining part of the heating wire, is found to have greater exibility such that that part of the heating wires which protrudes direct from the insulating material is no longer bent out of shape and breakage is avoided. An explanation is that the material of the heating Wires which, as a rule, is comparatively brittle, may, in addition, become less brittle due to the flattening operation. Whatever the explanation oi the effect of the embodiment of the invention may be the result proves to be efficacious.

It is known to construct supply conductors outside the tube as rigid contact pins and inside the tube as exible strips, the union between rigid :pin and ilexible strip being, for example. inthe seal. However, in the latter case, if thin wires were concerned, the phenomenon required to be v'avoided by the invention is liable to occur even with this known construction. However, owing to the thickness of the conductors, in this known construction cracking of the glass is more likely to occur than breakage of the conductors. Moreover, the material of such supply conductorslis not so brittle as that of thin heating wires. for cathodes. It is furthermore known to provide a grid stay Wire with a thin flexible connecting wire. Also in this case the above problem does not arise.

In order that the invention may be more clearly .understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which:

Fig. 1 shows a tube and Figs. 2, 3 and 4 are detail views of cathodes according to the invention.

Referring to Fig. 1, I designates the bulb of a tube, which is sealed by a bottom 2 in which contact pins 3 are sealed.

Arranged in the tube is an electrode system 4 comprising a bifurcated cathode 5 of the indirectly heated type constituted by a sheath 6 which is coated with emissive material and which forms an equipotential body (Fig. 2). The sheath 6 contains insulating material 'I and a heating wire 8 which is flattened at the end at 9. As is shown in Fig. 2, the flattened part 9 begins at a slight distance from the point at which the heating wire emerges from the insulating material, so that there is still a non-deformed part I0. Gwing to the great exibility of part 9, part IB does not bend, so that rupture at the area at which the wire emerges from the insulating material is prevented.

In order to assist in welding the ilattened end to a vertical supply conductor, this end may be torsioned as is shown in Figs. 1 and 2. However, in this case it is also possible to flatten the end of the heating wire for part of its length only and to leave the end II (Fig. 3) undeformed or several flattened parts (Fig. 4) may be provided, the heating wire end being flattened at several areas in various directions, so that it is adapted to be flexibly bent in all directions without the part II) being bent out of shape. Referring to-Fig. 4, parts 9 and I3 are ilattened in directions at right angles to one another, whereas part I2 may4 remain undeformed.

1t is obvious that even other embodiments of the invention are possible.

- 3 What I claim is: 1. An electron discharge tube comprising an envelope having a bulb portion and a base portion, an electrode structure including an indirectly heated cathode,b`ody'mounted in said bulb portion, an'outerconductive sheath on said cathode body, a .thin flexible heating wire in said sheath, and having an end portion extending out of said sheath at an extremity thereof, and amass-of compressed pulverulent insulatin'gjmaterial.llingf the space between said heating wire and said sheath at said extremity, a supply .conductor positioned on said base portion, said* thin;Y flexible:

heating wire having a iexiblecflattened portion electrically connecting said supply conductor and the said extended end portionof. said thin. ilexible heating wire.

2. An electron discharge tube comprising, an

blegflattene'd end portions at opposing ends therevoijelectricallyconnecting each oisaid supply conductors andvone of said extended end portions of saidthn ilexible heating Wire.

, 3,;,Ajnj electron' discharge tube comprising` an envelopieshvn'gra' bulb portion and abase portion, an electrode structurezincluding an indirectlly heated'V cathode body mounted in said bulb portion said body havingV a substantially U shape,

an' outer conductive'sheathon said cathode body,

agthin flexible heating'wire'in said'sheath and having opposingV end portions extending out of said sheath at opposite extremities of'said sheath,

a. massoicompressed pulverulent insulating material lling the spaces between said heating `wire and said sheath at each said extremity, and supply conductors positioned on said base portion, said thin iiexible heating Wire having Iiexible attened end portions .at opposing ends thereof lelectrically connecting each' of saidsupply veonducztors and one of said extended end portions of said thin flexible heating wire.

4-.- An. electron discharge tube comprising an envelope.- having an bulb portion and a base portion, an electrode-,structure including an indirectly heated .Cathode body mounted in said bulb portionan outer; conductive sheath on said cathode body, a' heatinglwire in said sheath and having an end thereof extending out. of said sheath at an.. extremity thereof, a mass .of compressed pulverulent insulating material filling the spacebetweensaid heating Wire and said sheath at said extremity, a supply conductor positioned on said base portion, a first flexible flattened member integral with said heating wire adjacent the said extended yend ofsa'id heating Wire; anda second iiexible flattened member integral with said heating wirefand electrically connectedlwith andextending at substantially right angles to' said-first attened member andinterposed between said first member and said supply conductor.

HENRICUS yJOHANNES DE WEYER.

REFERENCES CITED The followingY references are of record in the file of this patent:

UNITED STATESPATENTS Number Name Datel Re. 19,870 Lederer et al. Feb. 25,1935 247,097 Nichols'et al.' Sept.,13, 1881 1,914,883` Cottrell June20, 1933 1,968,280 Brian JulyBl, 1934 2,075,876 Von Wedel Apr. 6, 1937 2,399,402 Herzog June'lS, 1944 2,403,444 Hartman July- 9, 1.946 `2,403,4451 Liaco JulyV 9, 1946

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