US1894059A

US1894059A - Process for producing electron emitters and the product

Info

Publication number: US1894059A
Application number: US181944A
Authority: US
Inventors: Ruffley Frederick
Original assignee: FOREST RADIO Co DE
Current assignee: DE FOREST RADIO Co; FOREST RADIO Co DE
Priority date: 1927-04-08
Filing date: 1927-04-08
Publication date: 1933-01-10
Anticipated expiration: 1950-01-10

Description

Jan. 10, 1933. RUFFLEY 1,894,059

PROCESS FOR PRODUCING ELECTRON EMITTERS AND THE PRODUCT Filed April 8, 1927 Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE FREDERICK RUFFLEY, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO DE FOREST RADIO COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE PROCESS FOR PRODUCING ELECTRON EMITTERS AND THE PRODUCT Application filed April 8,

This invention'relat'es broadly to electron emitters. I

One of the objects of this invention is the provision of a coating compound for certain types of filaments to provide an efiicient electron emitter and especially one known as the Wehnelt' cathode. Y

A further object of this invention is the provision of a novel method of preparing the coating compound. I

A still'further object ofthis invention is the provision of a new and novel coating compound and the method of applying it to suitable heat producing bodies.

These and many other objects are successfully sought by means of this invention.

This invention resides in the combination of steps, construction, arrangement and relative location of parts as will appear more fully in the following description.

Referring to the drawing:

Figure l is a perspective view of one form of filament employing the principles of my invention, and

Figure 2 is a perspective view of a modified form with some parts broken away.

Heretofore in the preparation of electron emitting bodies for use in audions and similar devices it has been necessary to apply special treatment to the device while under construction in order to insure a complete removal of the gases therefrom without destroying the efficacy of the emitter. I have discovered a novel coating compound which, when applied to filaments of the proper type, results in an alloy filament which requires no special activation treatments such as electronic bombardment during the evacuation of the device in which it isto be used. The only type of treatment necessary is that of some temperature aging after the tube has been completed. One of the special advantages of a filament treated by the procedure of my invention is that a getter such as a magnesium flash may be employed to clean up the residual gases from the vessel without destroying the eificiency of the filament as an electron emitter.

The method of preparing the coating compound is as follows. A water suspension of 1927. Serial No. 181,944.

an inert substance such as magnesia or lime 1s mixed with: barium iodide and barium acetate. I have found that a water suspen- S1011 of a consistency of a thin paste is suitable for the purpose and one (1) gram of 5 magnesia or lime mixed with two (2) milligrams of barium iodide and one (1) gram of barium acetate will provide a suitable compound. I have found that all organic salts of barium are desirable for this purpose as, for instance, it is possible to use barium form-ate or barium .stearatein place of the barlum acetate. WVhen this coating compound has been prepared a suitable filament or heating body such as platinum or a platinum alloy comprising platinum and nickel or iridium is heated and coated therewith. I do not desire to be limited particularly to platinum or platinum alloy filaments since it is possible to use any metal which will alloy with barium for the purposes of this invention. In heating the filament I have found it best to heat the wire firstto a yellow heat to thoroughly clean it and then permit it to cool to a temperature where the body 2 5 is not visibly red and then dip the wire into the coating compound or otherwise apply the coating compound thereto. The heat in the body'of thewire is sufficient to drive off the moisture and leave the ingredients of the water suspension thereon.

This filament as prepared, is placed in any device employing cathode electron emitters and the vessel is exhausted by any of the usual and well known methods without treat- .35 ing the filament by electron bombardment during the evacuation. After the vessel is sealed off the filament is heated in the usual manner which results in a slow alloying action between the barium which. is easily 9'0 reducible from its compounds with the metal of the filament as, for instance, platinum. I have found that the inert substance such as magnesia or lime when employed in the mixture results in a slowing down of this alloy action which is desirable. The efliciency of a filament treated in this manner as an electron emittercontinuesover thefull life of the filament since whenever the filament is heated this slow alloying action is eontin- 100 ually going on with the result that the barium is being freed to alloy with the filament.

I have shown in the drawing two different forms of filaments constructed in accordance with my invention. The filament body platinum, platinum alloys'or other suitable body is shown at 1 to which has been applied the coating compound disclosed above in any suitable manner as by dipping, spraying, brushing, etc. The coating compound has been designated in Figure 1 by areference numeral 2. I In Figure 2 is shown a different form of filament that is well known as the VVehnelt type of filament in which the heating body is shown at 3 as a thin strip of suitable material such as platinum to which has been applied the coating compound 4 prepared as described above.

I am, of course, aware that many changes in the details of procedure and relative arrangement of steps, as well as in the ingredients and proportions thereof will readily occur to those skilled in the art, and I do not, therefore, wish to be limited to those quantities and materials disclosed by me for purposes of illustration, but rather to the spirit and scope of this invention as defined in the appended claims. For instance, any suitable metallic filament can be used with which the barium will alloy; any inert substance can be used in the place of the magnesia or lime; any of the organic salts of barium may be employed; the particular proportions by weight of the ingredients employed may be varied between reasonable limits and, finally, any method of coating the filament may be em loyed without departing from the princi of my invention.

hat I seek to secure by United States Letters Patent is:

1. The method of producing treated filamente com rising mixing together magnesia and organic salts of barium in water and coating a suitable filament with said mixture. 2. The method of producing treated filaments comprising mixing together magnesia,

barium acetate and barium iodide with water to form a paste and applying said paste to a.

suitable heating body.

3. The method of preparing electron emitting bodies comprising preparing a water sigpension in the form of a paste of magn a, barium iodide and barium acetate; heating a suitable body to clean it and coating said body with said paste while hot.

4. The method of preparing electron emitting bodies comprising preparing a water suspension in the form of a paste of one part by weight of magnesia, two parts by welght of barium iodide and one part by weight of barium acetate and coating suitable body with said paste.

5 A filament coating mixture comprising a water suspension of magnesia, barium O6 iodide and barium acetate.

6. A filament coating mixture comprisin a water suspension of one part by weight 0 magnesium oxide, and four parts by weight of barium acetate and barium iodide.

7 An electron emitting body prepared by having a coating of magnesia, barium acetate and barium iodide.

8. An electron emitting body comprising arbase of platinum and nickel alloy and a coating of mangesia, and organic salts of barium.

9. The method of preparing electron emitting bodies comprising preparing a water suspension in the form of a paste of magnesia, barium iodide and barium acetate; heating a body of platinum and nickel alloy find coating said body with said paste while 10. A filament coating mixture comprising barium iodide and organic salts of barium, and a material for retarding the alloying action of the barium with the filament.

In testimony whereof I have hereunto set my hand on this 29th day of March A. D.,

FREDERICK RUFFLEY.