US2037217A - Cathode - Google Patents

Description

p l 1936. w. W. EITEL All. 2,

CATHODE Filed April 17, 1934 l I /Z M 1 4 Hi IN V EN TORS.

WILL/AM w. f/TEL. JACK McCULLOUGH.

Patented Apr. 14, 1936 UNITED STATES PATENT OFFICE CATHODE William W. Eitel and Jack McCullough, San Bruno, Calif., assignors to Heintz & Kaufman, Ltd., San Francisco, Calif., a corporation of Nevada.

Application April 17, 1934, Serial No. 720,941

2 Claims. (01. 250 27.5)

Our invention relates to cathodes for thermior two kilowatts, are usually provided, due to the onic devices, and particularly to the form of such heavy currents handled, with a plurality of cathodes. cathodes or filaments connected together in Among the objects of our invention are: to parallel. An example of such a construction, and

provide an improved mounting for multiple filaone which is extensively used, is illustrated in ments of thermionic devices; to provide a mul- Figure 2 of the drawin t e ve V yp tiple filament construction which distributes ments being indicated by the reference numeral the electron flow therefrom more uniformly over 2. The free ends of the filaments are usually the anode surface; to provide a cathode construcsecured to a pa r of Spreader bars 3 Which a welded to the ends of leads 4 supported by the tion in which the heat drain from portions of the filaments is substantially eliminated; to prostem 6 of the tube. The shape of t e p vide an improved cathode onstruction which bars varies considerably in difi'erent designs of produces relatively greater electron emission than tube, some manufacturers preferring the Straight similar cathodes in present use; and to provide a yp as illustrated, and Others preferring U simplified and compacted multiple cathode conaped A ta d e150 Supported y the struction for thermionic devices. stem a point jac nt t e ads e e d p- Other objects of our invention will be apparent Wardly and i provided heal the p thereof W or will be specifically pointed out in the descripsuitable means for engagin the hights 0f the tion forming a part of this specification, but we filaments, Which means y Conveniently be a do not limit ourselves to the embodiment of the p of resilient arms 8 for tehsioning the fi ainvention herein described, as various forms may merits a d p v \With hooked portions 9 for be adopted within the scope of the claims. a g the tS er o Referring to the drawing: t It has been observed, under actual working Figure 1 is a perspective view showing the conditions, that when filaments mounted in this improved cathode of our invention as incorpofashion are heated, these Portions of each rated in a space discharge device and showing ment adjace t t e Spreader bars, as arbitrarily its relationship to other electrodes mounted indicated by the dimension A in u e l not therein. Parts of the view are broken away to be raised to the Same t p ure s t redisclose the construction more clearly. mainder of the filament. This is due to heat Figure 2 is a perspective view of the generally drainage from these portions of the fi a y practiced method of mounting multiple filaments. the Spreader bars and the terminals- It w In broad terms, our invention comprises th therefore, that maximum electron emission is combination, in an electrical discharge device t p oeu ab e from filaments mounted in the having, preferably, a substantially tubular anode; manner described. a tubular shaped control electrode comprising a Still another detrimental feature of such a plurality, of spaced vertically disposed conductors, construction lies in the fact that due to the close a cathode support comprising, preferably, a cyrelative spacing of each filament adjacent the lindrical standard in axial alinement with the bight thereof, that area of the anode nearest the anodeand control electrode, and a pair of spaced bight will receive a concentrated electron bomcathode terminals disposed adjacent the standbardment, while proportionately few electrons ard, of a cathode comprising a pair of filaments will fall on the areas of the anode farthest re-. secured to each other, and to a terminal, at the moved from the bights. In most instances, the ends thereof, the filaments diverging with rep w r b n h n y h tube is such that spect to each other from the terminals to a point this bombardment may be of sufiicient magnitude equivalent to substantially half of the length to cause serious overheating of the anode in the of the filaments, provided with bights at this areas subj c to the concentrated bombardpoint, and spaced apart a distance corresponding ment, with accompanying detrimental effect 011 with the spacing of the terminals, so that the the eiflcient operation of the tube.

filaments are disposed in angular relationship We have, by the provision of an improved with each other and are symmetrical in vertical planes displaced ninety degrees about a horizontal plane passing midway between the terminals and the bights.

' A great majority of the thermionic tubes designed for operation at powers of the order of one defects to a considerable degree, by providing for an increase in the electron emission from the cathode, by substantially reducing the heat drain at the attachment points and thereby, by such provision, creating a tube capable of sumounting for multiple filaments, obviated these perior performance. Furthermore, we have caused the filament wires to converge at the attachment points so that one wire will help heat the other. We have also succeeded in distributing the electron emission from the cathode more uniformly over the anode surface which permits greater heat dissipation by this electrode than is possible were it operating with the type of cathode generally used.

In greater detail, the preferred form of the improved cathode of our invention, and its relationship to other electrodes in a space discharge tube, is shown in Figure 1, in which the stem 6 is provided with the standard I and theterminals 4, the standard, at its upper end, being provided with the resilient arms 8 formed with thebight engaging hooks 9. An anode H and a control electrode 12 are shown surrounding the cathode.

The spreader bars 3 of the previously described construction have been dispensed with and the filaments 2 have been brought together at their ends and anchored by welding directly. to the ends of the terminals4. The terminals are preferably spaced apart a distance corresponding to the spacing of the hooks 9 so that each filament is disposed in relation to the other at the same angle as the angle of the legs of each filament between the bightand the terminals thereof. It will thus be seen that thecombined filaments are symmetrical in vertical planes displaced ninety degrees with a horizontal plane passing midway between the bights and the terminals.

Due to the elimination of the spreader bars the heat drain from the anchored ends of the filaments has been greatly reduced, in fact observations of a cathode constructedin this manner, under actual working conditions, failed to disclose a discernable portion of the filaments that was not heated to emission temperature. This, it is believed, isdue to'the heat radiating from the closely adjacent portions of the filaments near the terminals, assisting in raising the temperature of each other to a degree corresponding to other parts of thefilaments, and this together with the reduced heat drainage, provided by removal of the spreader bars, causes the filaments to be heated to emission temperature over their entire lengths between the terminals. It is obvious, therefore, that due to the substantial elimination of this undesirable heat drainage, the electron emission of thecathode, for a given exciting current, is-considerably increased, which increase re.- fiects itself in improved performance of the tube.

Another desirable feature, created by the arrangement of the filaments in this manner, is the symmetry of the cathode when it is viewed alternately from each end in positions rotatedninety degrees from each other. This provides, at the filament terminals, a similar condition to that existing at the bights thereof, in that the filaments are in the same spaced relationship at the two points. Thus the concentration of electron flow from the cathode to the anode H is similar at both ends of the latter electrode and, as a result of this, more uniform distribution of electrons is obtained over the surface of the anode and it is capable of dissipating the heat generated more rapidly, consequently the electrode is not likely to be overheated.

Still another desirable feature presents itself in that since the cathode assembly has been compacted, due to the removal of the spreader bars, the diameter of the control electrode l2, and also the anode I I, may be considerably reduced. This may readily be seen by referring to the drawing. The diameter of the smallest cylinder that could be placed about the construction of Figure 2, is slightly greater than the diagonal distance between the ends of opposite spreader bars, while the diameter of a cylinder that would clear the construction of Figure 1, is slightly greater than the distance between the outer surfaces of the terminals. This distance, it will be seen, is considerably less than the diagonal distance referred to in respect to Figure 2. The elimination of the spreader bars and the rearrangement of the filaments are also instrumental in reducing danger of arcing between grid and cathode.

The cathode just described permits the production of thermionic tubes possessing a higher degree of efficiency than was heretofore obtained in tubes of this character, permits a reduction in size of the tube elements, and due to its simplicity it may be constructed more economically and expeditiously.

We claim:

1. The combination, in an electrical discharge device having an'anode, a control electrode and a cathode support contained therein, said support comprising a pair of spaced cathode terminals, a standard disposed adjacent said terminals and resilient arms mounted on said standard, of a cathode comprising a pair of filaments joined together at their free ends and secured to said terminals, said filaments being looped over said resilient arms in spaced relationship, said spacing corresponding to substantially the spacing between the terminals.

2. The combination, in an electrical discharge device having a plurality of cooperating electrodes mounted therein including a cathode support, of a cathode comprisinga plurality of filaments provided with bights substantially midway between their free ends, said bights adapted to be supported by said cathodesupport, a free end of each filament being secured to a free end of another filament in a plane substantially ninety degrees out ofphase with a'plane passing through the bights of the filaments.

WILLIAM W. EITEL. JACK MCCULLOUGH.

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