US2372379A - Electron discharge device - Google Patents

Description

March 27,1945. H. K. ISHLER 2,372,379

7 ELECTRON DISCHARGE DEVICE Filgd May 19, 1943 "W i w: l a T574.

INVENTOR fikmwy KIN/v57 [SHLf/P ii N? The development of hearing Patented Mar. 27, 1945 UNITED STATES PATENT {QFFICE 1,372,379 if: ELECTRON mscnaac'nnnvron I Harry Kenneth Ishler, Emporium, Pa., assignor to Sylvania Electric Products Inc., Emporium, Pa., a. corporation of Massachusetts Application May 19, 1943; se ial No. 487,561 2 Claims. (Cl. 250217.5) I I This invention relates to electron discharge devices and in particular to the design of electron tube units of light weight and small dimensions.

Most of the various sizes and shapes of radio receivin tube types usual on the market about ten years ago have now been replaced by a single shape and size, considerably smaller than the average size formerly believed necessary for good performance. This form to which the older receiving tube types have converged is substantially that of a standard called lock-in tube. No serious demand for a smaller radio receiving tube seems to exist at the present time, and a proposed further reduction of size apparently did not correspond to any existing demand.

An actual need for a considerably smaller electron discharge tube existed, however, in applications other than radio broadcast reception. Representative of this demand are hearing aid sets, in which a reduction of the weight and size of amplifier tubes to the absolute minimum obtainable for the present status of the art is of immediate practical importance.

aid tubes has therefore led to a further improvement of the art connected with a considerable reduction of tube size, so that it is now possible to manufacture these exceedingly small tubes with practically no sensitivity against mechanical shock or handling. Accordingly, a principal object of the, invention relates to the reduction of the weight of theelectrodes used in extremely small electron discharge tubes. I y 1 ;A feature of the invention relates to a small .sizeelectron discharge tube in which the. heat radiation from the anode is increased, compared to the heat radiation obtained from a largersize anode in a tube of similar dimensions.

Another object is to 'providea plate construction whichcan be formed by simple punching and shaping operations on a singlesheet of metal.

According to another object of the invention,

means are provided to reduce the output capacity of a small filamentary electron discharge tube with a single strand filamentary cathode. Another principal object is to provide a plate construction for electron tubeswhich facilitates examination of the electrode assembly during or after manufacture, and the ancillary object of expediting the outgassing of the metal parts.

According to still another object of the invention, the ratio of the interelectrode capacity. between filament and control grid to that between filament and anode can be adjusted to any desired value within limits.

A feature of the invention relates an extremely small electron discharge tube having a minimum variation of input capacity over'a wide frequency band.

Another feature of the invention relates to a ru e o new method which permits the reduction of certaininterelectrode capacities of an electron dischargetube without increasing the size ofthe bulb or providing separate lead-in seals through different parts of the envolepe.

still further ieatureof the invention relates tures, each single. one o f which is, in the usual tube constructions obtained at the expense of some of the others. For example, the reductionof interelectrode capacitances may be achieved by the introduction of additional shielding electrodes (e. g., screen grids), which however, increase the weight and eventually the size of the tube. Or it by increasing the size of the en' maybe obtained velope and carrying the lead-in conductors through widely remote parts of the envelope.

-This not only changes the tube size but it also leads toundesirablesealing-in processes and may not be consonant withexisting circuit requirements. a

H filsually a reduction of the mass of the electrodes results in a decrease of the mechanical the tube, and a reduction of its ability .to radiate large quantities of heat at low temperature. According to the invention, means are provided whereby the mass of an electrode isdecreasedwhile its heat dissipation ability during-actual-use, issimultaneously increased. Or-

..dinarily, an increase of heat radiation surface of an electrode results in an increased size and weight of this electrode.

According to the invention, all these difficulties areavoided by anovel method of mounting and a change of shape of some of the electrodes, which permits a simultaneous achievement of these various ends without any sacrifice of space or simplicity of {the various other steps necessary for manufacturing a finished tube.

Theinvention will nowbe described in connection 'with the drawing, in which, A Fig. 1 is a cross-sectional view of a triode mount with filamentary cathode, built for high mechanical sturdiness, and provided with large radiating vsurfaceof the anode, correspondingto prior dei n -V I v Fig. 2 is a side view of the same triode mount. 1 Fig. 3 shows a cross-section through a similar triode,-but improved according to the invention.

Fig. 4 gives a side view of the mount of Fig. 3.

Fig. 5 is an elevational view of the plate shown in Figs. 3 and 4.

The triodemount illustrated in Figs. 1 and? consists of a header orstem'l through which are sealed lead-in connections 2, 3, 4, 5, etc. The plate 6 is supported by four plate support wires 1, 8, 9, l0, attached in any well-known manner to the mount spacers II and 12, preferably made of mica sheets. Also attached to these upper and lower mount spacers are grid supports; [3 and M, on which is wound the grid wire l5, also in a manner well-known in the art. Filament I6 is threaded through central holes the iin'oun't spacers, and the lower end of filament i6 is connected to one of the lead-in wires 3. The upper end of the filament held taut by him? corrvenient filament tension spring l1, the end of which is welded to filament tension spring sup-'- port [8, by means of a fi lainent tab 1 9.

The filament voltage may be applied to the filament l e at the rue-meat lead a and the filamen't spring support lead 2-0 as shown in the figure. It is of e'eur'se understood thatgfid and plate of the tube are i'sonhe-ted 't'o s'dl'he Cohveniently located lead in eendire'te'rs Knetshewn in the figure) in the header l.

Filament and grid ere completew susreunded by a box-like anode structure, whereby the grid structure is -electrostatically shielded by the anode from the filament tension spring "support. The -plate-t gri d capacity comparatively large,-due to the ra'ct that the grid is 'eemme'tely surrounded by the anode. This construction is very sturdy because oi the four plate supports and the sidewalls 2] 22, and "end Walls 2; 24, of the-plate hex, Which 'proV-l'd'es -grea't Stifiness to the plate structure. The' plate walls are solid surfaces and the oontihua-tions "2 5, -'26, 21

and 28 of the active plate walls {21 and 22, iii- *crea'se the radiation surface of the plate, so as to permit a. "greater heat dissipation. g

in Figs. 3-5 is 'sh'ow'n the new iis ih according to the invention, in which the plate sh'aiJ ahd the position (if the fila-mnt te'h's'ioh suppert are so modified as to result in a lowered plate *to id capacity, and an increased inherent capacity between the filament tension spring 18, and the grid I 5,while the -charactieristics*of the electron discharge space are not ch'an'ged com- "pared with the design or Fig. *1. It should noted that the large ih herhtoapabity resulting from the e1o'se ess of fileim'eht tension ratio of the effective interelectrode capacities between filament and grid on the one hand to that between filament and plate on the other hand, merely by shifting the position of filament support I8 along the dotted line arrows (Fig. 3).

The cooling of the plate is made more effective by bending the plate wings 29 and 30 outward and away from the discharge space much closer to the area of maximum electron dissipati'o'n near the gr-id laterals, as indicated by the full-line arrows which suggest the discharge path.

support 18 (in Fig; 1 to '-the=end'wall' 23 '61 the I plate is completely eliminatedfin the construetion shown in Figs. *3 and '-'rhe'distance between l8 and the plate wings29and 30in 3,

"reduces the output capacity very appreciably.

Inspection "er Figs. 1 the s also enews directly the way in which, according to the invention,

the low grid to 'filament -capacity=of Fig. this: i

stan'tially due to the shielding effect bfthe plate when located between fllafiner'it ttiiisioitt spring support I8 and grid 4 5) is inora'seti' in Fig. 3*by removing the 'shieldiii'g e'iid tv'a'll 28 hf the plate, and thus permitting some "o'f the electric lines of force from the suppcrt l8 t'o eiiddirectly on the grid 45, without interception.

Furthermore, reinoval "of this plate 'en'clytfa ll.

in Figs. 3-5, decreases the plate-*to 'grid "CQPMTW,

as compared with the closed box constructioii of Fig. 1.

Finally, it is obvious that in the construction er Figs. --3-5, it 'is always possible to 'adjus't the As may be seen more clearly from Figs. 4 and 5, the weight of the plate is appreciably reduced by openings in the wings and rib of the anode, which are not eleotiioally active in this "design.

1 It should be noted that the plate electrode in Figs. 3 and "4, is supported by only three plate supports 3|, 3'2 and 3'3, a "compared to the four plate supports needed in the prior design o'f'Fi'gs. l and '2. one might expect at first sight that the support has been weakened by the omission of one r 'theip'reviously used jplat'e supports. This is, however, not thecase, as will be easily understood from "the following consideration. The total weight of the anode of -Figs. 3- 5 is smaller thalh'that of the closed box-anode oi Figs. 1 and '2 for two reasons. 'The run length of the metal strip needed ffor forming the anode is shorter than that needed for forming the boxplate at Fig. 1. Furthermore, some of themetal stock of the new plate is eliminated by punching o'ut holes from the ribs and wings, as mentioned before in connection, withFigs. 4 and '5.

In one typeof tube oi this kind .actually being built, the total weight of ,theanode has beenreduced to about 60% ofi-ts original weight while preserving the other desirable characteristics of the .prior plate. I Accordingly, the load per plate support in the new construction is reducedto only of the weight which each one of the our plate supports :had to carry in the older design, even though the number of :plate supports has been reduced. It will be clear that the invention is not limited in spirit or scope to the iparticularembodiment disclosed, and that various changes and modifications can be .made therein as will he apparent afterconsiderihg the foregoing description and the appended .claims.

WhatI claim is: I

-1. An electrode fo'r electron d-lscharge tube's, comprising ametal strip beht to tennis. troughlik'eshape in "transverse section, the edges of the trough being bent back and iormin'g' diverging wings the main trough-like portion being Zunperforated to act as an electron receiving electrod'ean'd said bent back'wings be'in'g perforated, and tesuppor t the electrode adjacent the edges of said wings arid-adjacent the b'a'se of salid trough, *sa'id supporting 'r'ri'eans being positioned --in'-triangular -array, I I

2. -'A ftub'e mount comprising a header carryin'g a plurality o'f- "electrode-suppcrtrods, -'a pla'tehlectrode supported-on three of sa'i'd rods arranged an triangular array, said plate being of meta'lb'ent back upon itself to-form a *constric'ted -'chan'nl to receive one -o'f sail rods *and an enlarged "trough-like section serving as {an electron ohahrber, the edges of said trough-likes'ectioh bein'g gbent back andoutWa'rdIy 'diverg'ing and'attached to respective support rods. I "ISHLE' R.

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