US1840284A - Electron discharge device - Google Patents

Description

Patented Jan. 5, 1932 SYLVESTER W. CROWLEY, OF WEEHAWKEN, NEW JERSEY, ASSIGNOR TO .IDE FOREST RADIO TELEPHONE 8c TELEGRAPH (10., OFJERSEYOITY, NEW JERSEY, A CORPORA- TION OF DELAWARE d No Drawing Application filed March l,

This invention relates to electron discharge devices and more particularly to'the means by which the same are exhausted. Theobjects of the invention are to enable an electron discharge device to be manufactured in less time than heretofore; to reduce the time and expense involved in obtaining a high degree of evacuation of the device; to employ a chemical clean up agenc for obtain-ing part of the .evacuationyto employ a flash as wellas a chemical clean up agency; to employ a chemical clean up agencyand flash adapted to be applied simultaneously and put into effect at d fferent times; to enable the chemical clean up agency and flash to be put into eflect by'use of high frequency or by platefbomba-rdment; to obtain' an'improved method of manufacture; to secure simplicity of construction roperation,.and to obtain other advantages and results as may be brought out in the following description. Q o

In the manufacture of electron discharge devices, it has become moreor less {common practice to employ-a fllamentwhich includes the element thorium ,as the emissive substance. Thorium oxidizes quite readily and consequently the filament as inserted in an electron discharge device contains exposed portions of thorium oxide rather than pure thorium. In order to reduce'thorium oxide to thorium, it has become common practice 7 to employ a flashof some suitablematerial,

of which magnesium is the one most generally used. The operation is ordinarily carried out "by applying a small portion of magnesium' to the plate and then after the tube is evacuated as much as possible by the pump, the plate is heated to a point where the magnesium will flash and the resulting vapor will operate to reduce the thorium oxide to' thorium. The present invention contem plates means for first obtaining a partial vacuum by means of a pump so' as to materi'ally reduce the'time' during which the electron discharge 'device has to be connected withthe pump for the purpose of evacuation, and then evacuation is obtained by other means, after which the magnesium or other material may be flashed similar to the 7 carried on heretofore.

ELECTRON nrscnanen DEVICE 1924. Serial No. 696,396.

manner in'which that operationhas been In order to obtain the high vacuum-by means other than by pumping, I employ a chemical which is flashed similar to the magnesium, preferably before the magnesium is flashed, said chemicalobtaining a high stateofevacuation of the tube by means of reduction of the residual gases Within the tube. ,The magnesium could not be used practically for this purpose, both because it is not sufliciently active to reduce the residual gases to the necessary amount nor is it-practical to flash the magnesium until a very muchhigherdegree of evacua tion has been ,efl'ected than is required'in connection with the [present invention.

I preferably employ in combination with a flashof magnesium'or othersu-italblematerial; p

chemical cleanup agency of phosphorus;

The advantage of employing phosphorus is v that it may be flashed at a lower temperature than magnesium and also that phosphorus will eflectively reduce-the residual gases when flashed while the device is not in such a high state of evacuation as necessary to obtain reduction by means of magnesium. I may also state, that very good results are obtained'by use of red or amorphous phosphorus. Since phosphorus in this state is much more con venient'to handle and does not have to be protected until ready to "be flashed, itis the better variety to use. r 1 f- In order to applythe phosphorus to the plate or other partfrom which it is to' be flashed, I preferably mix the phosphorus and magnesium in the-nature of a paste or paint and apply it with abrush'or in any other suitable manner. As much of the plate as desired may be covered with themixture,&although it will probablybe suflicientin most cases to employ only a good sized spotonthe plate. '-I do not wish it to be understood that it is necessaryto mix the 'phosphorus'and magnesium, and indeed, in some instances,

it'maybe highly desirable not to mix the two;

[The flashing of the phosphorus and magnesium, as indicated 'above, takes place Fat different timeaphOsphorusFbeing flashed first in order to reduce the residual gases and obtain'fa higher degree of evacuationQa-fter' Whichthe magnesium'is flashed in order to reduce the thorium oxide of the filament to thorium. There are a number of Ways of obtaining the flash of the phosphorus and magnesium, one instance ofvvhich is the usual method of plate bombardment. Thetemp'erature of the plate is raised by -means of an initial electron emission to such aj point as to cause the phosphorus to vaporize-and 'combine with the residual gases; Continued bom- V bardment of the plate will raise the temperature to a higher degree and thus obtain a subsequent flashing of the magnesium. 'The flashing of magnesiumhas heretofore been effected by means of hi' h frequency current, and this may also beutllized for flashing the phosphorus. In order to .obtain' a marked time difference betweenthe flashing of the phosphorus and magnesium, the phosphorus maybe applied to the ,platetoward one end of the electron discharge device and the mag nesium applied to the plate toward the other end,so that the high frequencycoil may be manipulated to operate only ontheendof the plate to which the phosphorus is applied, so

as to flash the phosphorus and then moved alongso as to-operate upon the other end of the plate and flash the magnesium. It is apparent that both the phosphorus and-the magnesium provide clean up agents both of which are flashed but at rdiflerent temperatures. In the broad aspect, of this invention any tvvosuitable-agents couldbe used which are adapted tobe flashed at different temper- The term flash, as. used-inthe claims, relates to the clean up agentadapted' atures.

to be activated at the higher temperature.

I ,Obviously other detail changes and modifications may be made in the manufacture and use of my improved electron dischargedevice,

and I -do not-Wish to be understood aslimitprlorarta, 3

Having thus; described I my invent on, claim: r V

ingfmyself to the exact structure or .method described, except as set forth inthe follow: ing claims "when construed in 1. An electron discharge device: having applied thereto in the course of V manufacture a mixture-of phophorus and magnesium.

-2. A;method of manufacturing, electron discharge devices consisting in applying a mixtureof a chemical clean up agency and a: flash {to the plate, and flashing the chemical clean upf agency and flash. at different times, r

.3. A. method of manufacturing electron.

discharge devices consistingin applying .a

mixture of a chemical clean up agency and a flash to theplate, and flashing the chemical cleanup agency andsubsequentlyflashing the .4. In anlelectron ;,discharge device the bination of a illlflIIlQIll) containing. thorium, Pla .e e Qdehav g; thereon-fie an-up the lightlof the clean-u agenti'on the:interiorio' said device;

the I clean-gu ia'gentibeing Iendered' eifectiVe prior to the activation'of saidflash fo'r reducjin the vacuum in said device to a point rej-qu1s1te'fo'rtheproper action of said flash.

6. An electron discharge devicenccorgh ing to claim 5 in whichsaid clean-11p agent includes phosphorus.

and aclean-up agent eflectivetofclean u the gases within said device prior tothe'actlvation of said flash.

7. An electron discharge device a I ,thoriated filament, a flash materialcontain ing magnesium for activating said filament V 8. The methodof manufacturing an use tron discharge device having athoriated electron emitting filament jwhic hcomprises applying a chemical clean-up agent and a V filament activatingflash materialjon the in terior of the -device, and flashing the "cleanup agent priorto the flashing of -the filament flash material. p: V

9. The method of manufacturing anelectron discharge device having a thoriated electron'emitting filamentlconsistin'g in apply ing chemi a e w a nt a e nesium filament activatingfflash to the plate, flashing the clean-up agent :to reduce the evacuation'to a point where theifil am entflash vvill be eflective and then flashing the flash. 1.10. The method of manufacturingthoriat nation which comprises first flashing the phosphorus to reduce the evacuation to a ed 7 filament lelectron discharge devices employing phosphorus and magnesium for evac} point where the magnesium can be 'efiectively flashed to activate {the filament, 1 and then flashingthe magnesium to activatethefila-, I

v V, p I; j 11. The process ofexhausting electrondischargedevices; having thoriated electron e tin l me w e l d the epze bringing th'e plate to onetemperature rendera clean-up agent eflective, and {subse{ quently bringing. the; plate to a higher. tern flash-.material. 1

perature toactivate a 'filament activating 12'. The process ofexhausting anielectron discharge; device;,.of thethoriated filament type; employinga chemical clean-up, ag nt- ,and agrnagnesimn flash' on the platevvhicli comprises-bringing the plate; toone-tem P ra ure a tef h'etcl p-a n a d i u s q en y a s a t pera ur of-the,

plate when} the requisitedegreegof vacuum iii? has. be ncattained flash" said magnesium 13. An electron discharge device having an electron emitting member in the form of a thoriated filament a plate having applied thereto a clean-up agent containing, phosphorus, and a magnesium filament activating flash, and means including said emitting member for bringing said plate to one temperature to render said clean-up agent efiec- ,tive and for subsequently raising the temperature of said plate to flash said magnesium to activate the filament.

14. An electron discharge device of the thoriated filament type having a chemical clean-up agent of amorphous phosphorus, and a filament activating flash material of magnesium.

15. An electron discharge device having an electron emitting filament containing thorium, said device having applied thereto in the course of manufacture a mixture of a chemical clean-up agent containing phosphorus, and magnesium for activating the thoriated filament.

SYLVESTER W. CROWLEY.