US1757233A - Discharge tube - Google Patents

Description

May 6, 1930;

C. BOL bIS'CHARGE TUBE Filed Sept 30 1924 Patented May 6 1930 I UNITED STATES'PATENT OFFICE CORNEIJIS BOL, OF EINDHOVEN, NETHERLANDS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO RADIO CORPORATION OF AMERICA, OF NEW YORK,

NEW YORK N. Y., A CORPORATION" OF DISCHARGE TUBE Application filed September 30, 1924, Serial No. 740,738, and in the Netherlands October 17, 1923.

- This invention has reference to incandescent cathode discharge tubes, especially to discharge tubes of the said kind, the operation of which is essentially based on elec- 5 tronic motion.

In incandescent cathode discharge tubes in which the electric discharge takes place practically entirely or essentially by electronic motion, or in other words in which positive 10 ionization does not practically occur or only to a very little extent, the electrons are deflected from the course they would follow exclusively under the influence of the electric field by the action of the magnetic field arising around the current carrying incandescent wire. This phenomenon becomes particularly important when the discharge tube is intended for very great capacities and in this connection the diameter of the incandescent wire becomes large, for example materially over 1 millimetre. I

If for example in a high vacuum rectifier which contains a straightly stretched incandescent wire and a cylindricalanode coaxially arranged therewith a voltage is supplied between the incandescent cathode and the anode, the electrons emitted by the incandescent wire would move radially from the incandescent wire to the anode if they were not deflected from that course by the magnetic field surrounding the incandescent wire. By reason of this deflection it is essential that the voltage supplied between the anode and the cathode should lie beyond a certain a do not reach the anode but return to the incandescent wire.

When the thickness of the incandescent wire becomes considerable and in. this connection the incandescent current very heavy, the said deflection may become so large'that difiiculty is encountered in constructing the tube, as the minimum value referred to of the voltage. becomes high and comes to lie beyond the intended voltage of operation.

The invention has for its object to cause the magnetic field referred to to disappear or at least to materially weaken the same by a particular construction of the cathode 5 and also to insure a very solid arrangement minimum value as otherwise the electrons of the incandescent cathode coaxially with other cylindrical electrodes.

In discharge tubes according to the inventron the incandescent cathode consists of a tube inside of which is a conductor, the tube and the conductor being so shaped and arranged relatively to each other that the magnetic fields generated by currents of equal strength and flowing in the tube and in the conductor in opposite directions neutralize or at least materially weaken each other outside the tube. The conductor provided within the tube may consist of one or more wires.

According to the inventionmeans may be provided for cooling the conductor.

The incandescent cathode accordingto the invention may preferably consist of a tube having an annular cross-section, a conductor being substantially coaxially arranged inside said tube, the tube and the conductor being at one end in conductive connection with each other.

According to the invention the conductor in the tubular incandescent cathode may be The rectifier shown on the drawing conformed into a tubular aggregate. The incandescent cathode may be superficially coated with substances that easily emit electrons, for'example, with one or more oxides of material, prefthealkaline earth metals and the tube itself may in this case be constructed of material having a lower melting point than tungsten, such for example as platinum or nickel.

The tube 1 is on one side in conductive connection with a conductor 3. For, this purpose the conductor may at that place be provided with a flared out or expanded portion 2 which is sealed-to the tubular cathode. The conductor 3 is substantially coaxially arranged in the tube and may consist of material which is a good conductor of electricity, such for example as nickel or copper. It will however frequently be essential to also make the conductor 3 of tungsten. The conductor 3 and the tube 1 must be adapted to carry a current of e ual strength. The crosssection of the con uctor 3 is chosen that the temperature of t e latter during the operation of the tube remains lower than of thetubular cathode 1. The conductor 3 is clas ed within a binary strap 4: as indicated in igure 1, which strap may consist of nickel and is connected in any way for example by soldering, to two metal caps 5 hermeticall sealed at the edge to the ends of glass tu es 6. Thecaps 5 have fixed to them leading-inwires 7. Suitable material forthe said caps is chrome iron of such composition thatits coeflicient of expansion corresponds to that of the glass. When using for example potassium soda glass, the content of chromium may be about 17 to 20%. On the other side of the caps 5 are secured-the leadin -in wires-7.

he tubular incandescent cathode 1 is clasped within a binary strap 8 secured to two caps 9, which in their turn have fixed to them leading-in wires 10. The'caps are hermetically sealed t6 glass tubes 11 and may consist for example 0 chrome iron of suitable composition. The glass tubes 11 and the tube 5 form part of a glass sealing member 12 which at the edge is hermetically sealed to the end of avessel 13 serving as an anode. This vessel may at the place of sealing consist of chrome iron of suitable. composition, and preferably the entire vessel is made of chrome iron. The vessel 13 is cylindrical and coaxially arranged relatively to the incandescent cathode 1. It is provided with a thread 14 by means of which the discharge tube'can be located in a vessel through which a cooling'liquid for thejan'ode 13 flows.

' The conductor 3 shewn in Fi re 2 is made hollow and has arranged inside a tube of small diameter'15 for t e supply of the cooling medium. The conductor 3may in this case be connected directly to a ca 16 which has fixed to it a leading-in wire 1%. In this case the leadin -in wire17 should'be hollow so as to allow or the passage of the tube 15.

It is obvious that with the constructions of the incandescent cathode according to the invention shewn on thedr'awing, no magnetic referably so fields arise outside the incandescent cathode and that consequently the electrons'under the influence of the electric field prevailing between the incandescent cathode and the anode will move at least approximately radially.

I claim: 4

1. A discharge tube having a tubular incandescent cathode, a hollow conductor disposed substantially coaxially within said tubular cathode, said conductor and said tubular cathode being at one end connection with each other, and means for cooling the said hollow conductor.

2. A discharge tube having a cylindrical anode member forming a portion of the outside wall of said tube, a base portion for said tube and an. air-tight connection between said base portion and said anode member, a tubular cathode member extendin coaxially of said anode member contained within' said tube closed by said anode member, means for supporting said tubular cathode within said tube and rigidly fastening the same, connections for supplying current to said tubular cathode passing through said support means,

and base member, a second tubular member contained within said tubular cathode and in conductive relationship therewith at one end, and means for rigidly mounting said second tubular member within said cathode and establishing a current connection therewith, said tubular'cathode and said inner conducting tube providing means for neutralizing magnetic fields produced by current flowing through said members whereby electronic emission takes place in a radial direction between said cathode and anode.

3. In a discharge vessel, a cylindrical anode member, a glass support means for said anode of like diameter to said anode, means for hermetically'sealing said glass support means and said cylindrical anode to form'an evacuated envelope, a tubular cathode supported within said cylindrical anode andarranged coaxially with respect thereto, a plurality of connections between said glass support member and said gathode for supplying current to said cathode and rigidly mounting the same, a tubular member within said cathode for completing the cathode circuit and permitting currents to flow therethrough in an opposite direction to the direction of flow through said cathode,

in conductive Ill means for establishing electrical connection with said inner tubular member, "means for rlgidly supporting said last named member from said glass support, and a' connection between said tubular cath- ,ode and said inner tubular member at theend of each member remote from said support members, said tubular cathode and inner tubular member providing means whereby currents flowing t erethrough produce magnetic fields in opposite directions so that the field outside said tubular cathode is neutralized and electronic emission takes place between said cathode and said anode in a radial direc-. tion. s

4. In an electronic discharge arrangement, a glass supporting member forming a base for the discharge apparatus, a tubular anode member, said member being of like cross-sectional size to said glass support member and means for fastening said glass support member to said anode and providing an hermetim cally sealed body, a tubular cathode within said hermetically sealed body, a binary strap carried by said glass support for rigidly mounting said tubular cathode coaxially with respectto said anode, means for sealing said strapto said glass support, said strap providing means for establishing a current connec-. tion for said tubular cathode, a second binary stra supported from said glass support, and

a tubular member carried thereby and rigidly supported within said tubular cathode, said tubular member and said cathode being in conductive relationship with respect to each other at the end remote from said support, said cathode and inner tubular member providing means for producing opposing ma net-ic fields external to said tubular catho e upon a flow of current therethrough, whereby the magnetic field external to said cathode is neutralized and electronic emission takes place in radial direction from said cathode to said anode.

v 5. The arrangement claimed in claim 4 comprising, in addition, a tubular cooling member contained within said last named tubular member and means for introducing a cooling fluid within said coolin member for maintainin said tubular memger contained within sai cathode at a temperature below that of said tubular, cathode.

o In testimony whereof I 'aflix my signature, atthe city 0 Eindhoven, this 3rd day of September, A. D. 1924. 7

' CORNELIS BOL.

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