US2426255A

US2426255A - Cathode for electron discharge devices

Info

Publication number: US2426255A
Application number: US613455A
Authority: US
Inventors: Widmaier William
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC; Federal Telephone and Radio Corp
Priority date: 1945-08-30
Filing date: 1945-08-30
Publication date: 1947-08-26
Anticipated expiration: 1964-08-26
Also published as: GB616712A; BE472665A; FR938873A; CH265652A; NL66444C; ES176810A1

Description

Au -2e, 1947.

w, WIDMAIER 2,426,255

CATHODE FOR ELECTRON DISCHARGE DEVICES Filed Aug. 30, 1945 ATTO R N EY Patented Aug. 26 1947 CATHODE FOR ELECTRON DISCHARGE DEVICES William Widmaier, Elizabeth, N. J., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application August 30, 1945, Serial No. 613,455

18 Claims.

This invention relates to electrodes for electron discharge devices and more particularly to the wire mesh or metal strip type of cathode structures as employed in gas or vapor types of rectifier tubes of high current carrying capacities.

The improved emitter structure of the invention is designed to produce a high degree of electron emission with a minimum expenditure of heating energy and to provide a cathode structure of large electron emission surface areas with relatively reduced heat radiation. Because of its regenerative properties, the filament operates at substantially a uniform temperature over its entire length-to a much greater degree than other similarly shielded filamentary type cathodes. It is of a formation and assembly offering structural or mechanical strength such as to be rigidly self-supporting and to resist deformation under the infiuence of heating in its operation such as might impair the proper emission characteristics. It is further designed to be particularly compact offering advantages in its structural embodiment and with the further advantage of permitting its being made of very thin metal to have high resistance values while maintaining the required mechanical strength for efficient operation over long periods of use.

In addition to its desirable self-supporting rigidity, the improved emitter is of a structural design which maintains the general shape and relative position of the electron emission surfaces substantially constant irrespective of the expansion and contraction under temperature change so as to maintain its electrical characteristics constant under variable operating conditions.

The aforesaid structural and operational advantages are successfully attained by an improved emitter electrode or cathode structure composed of strips of metal which are folded along transverse lines alternately with reverse folds. The resulting strips of accordion pleated form are interfolded with the strips positioned in relative angular relation with interweaving to effect alternate positioning of the panels or plane sections.

The developed structure produces a fabric strip type of electrode composed of two strips in interlocked and intersupporting relation of such character as to materially strengthen the resulting structure against lateral forces such as magnetic pull and likewise to resist deflection or sagging under heated condition of use. The structural reinforcement by the interfolding of the strips accordingly obtains the benefits of the mechanical strength of the metal fabric on edge in two directions thereby avoiding the weakness of single strip corrugated or pleated formations of metal strip electrodes as heretofore proposed. As will be appreciated the strengthening effect as thus contributed permits of employing wire fabric strips of extremely fine gauge wire and fabric thickness with proportionate reduction of current consumption.

The described and other features and advantages of the present improvements will be more fully understood by reference to the accompanying drawing wherein like reference characters are applied to the corresponding parts in the several views.

In the drawings:

Fig. 1 is a perspective view of a portion of the improved electrode structure composed of metal strip interfolded or interwoven in angular relation;

Fig. 2 is a perspective view showing the folded strips separated and in their angular relation for interfolding;

Fig. 3 is a View partially in central vertical section and partially in elevation illustrating an embodiment of the invention in a gas filled diode type rectifier tube and Fig. 4 is a detailed vertical sectional view illustrating the mounting of the electrode in end elevation.

Referring to the drawings wherein there is disclosed one embodiment of the invention as illustrative of the principle employed in the production of the improved type of metal strip electrode, the emi ter is shown employed as the cathode of a gas filled diode-type rectifier tube which may be of the mercury vapor type. The improved cathode structure in accordance with the invention is preferably made from strips l and 2 of metal fabric which may be of fine gauge nickel wire coated with thermionically active material such as barium, calcium and/or strontium oxides. The metallic strips, of elongated ribbon form and of uniform width, are in their preparation initially folded as indicated in Fig. 2 upon equally spaced transverse lines. The spacing corresponds substantially to the width of the ribbon or strip and these folds 3 are made or turned successively in opposite directions to produce a resulting folded ribbon of zig-zag or accordion pleated progression. Two of the strips thus folded are relatively positioned with their folded edges in angular relation as illustrated in Fig. 2 showing the respective strips in their angularly displaced relation for interfolding to complete the cathode structure.

With the strips l and 2 thus angularly disposed they are interfolded as shown in Fig. 2 by interweaving wherein the folds or bends of each strip embrace or enfold a free edge 5 of the formed rectangular panels 5 of the associated companion strip. In this mutual interfolding of the strips as shown the folds or bends of a given strip embrace free edges of the panels of the other strip alternately at opposite sides so that a rigid type of interlocking is effected and wherein as will be noted the metal on edge relation of the respective strips is angularly disposed in 90 angularity upon compression of the folded structure. In consequence there is metal fabric on edge strength effective in angularly disposed transverse directions thereby adding considerable strength to the assembled structure.

In the completed assembly of the emitter structure as shown in Fig. 1 the rectangular panels formed by the folding assume an acute angular relation with relation to connected adjacent panels. There is thus provided a close spaced relation of the emission surfaces. This is as would be effected on elongation or expansion of the structure from a flat folded relation with the panels in face engagement.

The disclosed interfolded structure in addition to its rigidity has a materially enhanced filament efliciency resulting from the permissible use of fine gauge fabric and a greater degree of compactness resulting in decreased heat radiation. It further has maximum emission areas thereby to obtain high thermionic cathode efiiciency by a close spacing between the panel emission surfaces which spaces are of a formation to make the structure regenerative.

An illustrative embodiment of the improved emission electrode structure is shown in Fig. 4 wherein the emitter is employed as a cathode of a thermionic gas filled diode rectifying tube.

In the structural arrangement as shown, the tube which may be of the type employing ionizable mercury vapor comprises the customary base 6 containing insulatingly supported terminal pins 1 connected by wires 8 to the tungsten lead supports 9. The supports have spaced upper ends upon which the cathode is supported and connected by having its ends composed of the two strip layers of wire mesh material, welded thereto. Supported above the cathode in suitably spaced relation is the anode IE1 of inverted cup formation. Surrounding the cathode and its mounting is the usual filament shield l l secured to a shielding disc support l2 mounted upon a central supporting rod l3 supported within the lower press l 4. The upper end portion l5 of the shield is of reduced cylindrical form extended within and in spaced relation to the anode to provide the usual upper vent for the ionizing chamber 16 within the shield. The anode is connected to an output lead I! connected to the upper terminal l8 supported upon the reduced end IQ of the usual glass envelope 20 containing the mercury vapor charge. Insulatingly supported upon the leads and positioned in spaced relation below the shield is a lower heat shield 2| upon which the usual getters 22 containing vaporizable magnesium are supported as shown. In this disclosed embodiment of rectifying tube the cathode of the improved structural formation as described is mounted as shown to be positioned edgewise relative to the anode or target surface. The cathode may be mounted other than as shown to suit specific conditions.

While the invention is described with respect ,4 to a desirable embodiment of the features thereof it will be understood that varied modifications may be made therein without departing from the scope of the invention as defined in the appended claims. As illustrative thereof while the method of making refers to the initial folding of the strip or ribbon lengths to provide a reverse fold strip with subsequent interfolding of the strips it will be understood that in manufacture the strips may be folded and interwoven as a, progressive operation simultaneously to produce the assembled and finished product. Also while two strips are employed in the preferred structure as shown, three or more strips may be interfolded in similar manner with resulting change in form of the panels. In the instance of the interfolding of the three strips a hexagonal composite panel formation will result as is readily understood.

What is claimed is:

1. An electrode consisting of metallic strips folded on substantially transverse lines with progressive reverse bends and having the strips interfolded in angularly disposed relation.

2. An electrode as claimed in claim 1 wherein the strips are of metallic mesh material,

3. An electrode as claimed in claim 1 wherein the strips are of metallic fabric coated with thermionically active oxides.

4. An electrode consisting h of metallic strips folded on substantially transverse lines with successive reverse bends and having the strips interfolded in angularly disposed relation with the formed panels extended into angular spacing relation.

5. An electrode consisting of multiple strips of wire mesh material reversely folded on substantially transverse lines with successive reverse bends to be of zig-zag form and having the strips interfolded in angularly disposed relation with the formed panels disposed in acute angular relation.

6. An electrode consisting of metallic strips reversely folded on substantially transverse lines with qually spaced and successive reverse bends and having the strips interfolded in angularly disposed position with the formed panels disposed in acute angular spacing relation.

'7. A cathode for electron discharge devices consisting of metallic strips folded on transverse lines with successive reverse turns and having the strips interfolded in angularly disposed relation to present strip material on edge in planes disposed at substantially ninety degrees angularity.

8. A cathode for electron discharge devices consisting of strips of metallic mesh material folded on transverse lines with successive reverse turns and having the strips interfolded in angularly disposed relation to present strip material on edge in planes disposed at substantially ninety degrees angularity and having its resulting panel in acute angular and spaced relation.

9. A cathode for electron discharge devices consisting of multiple strips of wire mesh material folded on substantially transverse lines with successive reverse bends and interfolded in angularly disposed relation of the strips to present strip material on edge in planes disposed at substantially ninety degrees angularity and with expansion of the structure to position the resulting panels in angular and spaced relation and said strips being coated with a thermionically active oxide,

10. A cathode for electron discharge devices consisting of multiple metallic strips reversely folded on substantially transverse lines and interfolded angularly disposed relative to one another with the bends of each strip embracing the free panel edges of the companion strip alternately at opposite sides thereof and having the resulting panel formations in angular relation.

11. A cathode for electron discharge devices consisting of two metallic strips reversely folded on equally spaced transverse lines and interfolded to be angularly disposed relative to one another with the bends of each strip embracing the free panel edges of the companion strip alternately at opposite sides thereof and having the resulting panel formations in acute angular relation.

12. A cathode for electron discharge devices consisting of two metallic mesh strips folded on transverse lines with successive reverse bends and interfolded in angular position relative to one another With the bends of each strip embracing the free panel edges of the companion strip alternately at opposite sides thereof and having the resulting panel formations extended into acute angular spacing relation and said strips being coated with thermionically active material.

13. The method of making electrodes for elec* tron discharge devices consisting in reversely folding strips of metallic material on transverse lines and interfolding the strips angularly disposed relative to one another with the bends of each strip embracing the free panel edges of the other strip alternately at opposite sides thereof.

14. The method of making electrodes for electron discharge devices consisting in reversely folding strips of metallic material on equally spaced transverse lines and interfolding the strips angularly disposed relative to one another with the bends of each strip embracing the free panel edges of the other strip alternately at opposite sides thereof.

15. The method of making electrodes for electron discharge devices consisting in reversely folding strips of metallic material of uniform width on equally spaced transverse lines and interfolding the strips angularly disposed relative to one another with the bends of each strip embracing the free panel edges of the other strip alternately at opposite sides thereof and with the formed panels in angular spaced relation.

16. An electron discharge device comprising an enclosing envelope, electrodes supported within the envelope in spaced relation including an anode and an electron emitting ribbon cathode formed of multiple strips each of which is folded on transverse lines successively in reversed direction and interfolded in angularly disposed relation of the strips With the formed panels in angular and spaced relation providing a cellular structure, said cathode being supported with an edge of the rectangular structure directed toward the anode, input leads to the cathode and an output lead connected to the anode.

17. An electron discharge device comprising an enclosing envelope, electrodes supported within the envelope in spaced relation including an anode and an electron emitting ribbon cathode formed of multiple wire mesh strips each of which is folded on transverse lines successively in reversed direction and interfolded in angularly disposed relation of the strips with the formed panels in acute angular and spaced relation providing a cellular structure, said cathode being supported with an edge of the rectangular structure directed toward the anode, input leads to the cathode and an output lead connected to the anode.

18. An electron discharge device comprising an enclosing envelope, electrodes supported within the envelope in spaced relation including an anode and an electron emitting ribbon cathode formed of multiple strips of wire mesh each of which is folded on equally spaced transverse lines successively in reversed direction and interfolded in angularly disposed relation of the strips with the formed panels in acute angular and spaced relation providing a cellular structure, said cathode being supported with an edge of the rectangular structure directed toward the anode, input leads to the respective ends of the cathode, an output lead connected to the anode and said strips being coated with a thermionically active oxide. 1

WILLIAM WIDMAIER.

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

UNITED STATES PATENTS Number Name Date 21,222,021 Etzrodt Nov. 19, 1940 1,913,432 Denzler June 13, 1933