US2538054A - Chromium sulfate coated electrode - Google Patents

Description

Jan, 16, 1951 E. K. SMITH I 2,538,054

CHROMIUM SULFATE COATED ELECTRODE Filed Sept. 10, 1949 FIG. 1.

' NON-EMISSIVE RADIATING comma E. K. s m??? Patented Jan. 16, 1951 CHROMIUM SULFATE COATED ELECTRODE Earl K. Smith, West Orange, N. .L, assignor to Electrons, incorporated, Newark, N. .l., a corporation of Delaware Application September 10, 1949, Serial No. 115,102

Claims.

This invention relates to electron discharge tubes, and more particularly to a surface film or coating for the electrodes of such tubes to facilitate heat: radiation and reduce electron emission from the electrode surface at its operating temperature.

One problem in the design and construction of electron discharge tubes, more particularly tubes having the higher current ratings, is that the anode and the control electrode tend to assume a high temperature in operation and emit electrons to a degree to interfere with the proper performance of the tube. For example, during operation of a gas tube with the higher continuous current rating, the anode tends to assume a high temperature due to bombardment by the electrons of the discharge current; and excessive electron emission from the anode at such elevated temperature tends to reduce the negative or inverse voltage which the tube may stand without an arc-back or discharge through the tube in the wrong direction. Similarly, the control element or grid in such a tube tends to assume a high temperature due to heat radiated from the anode and from the heat shielded cathode, and excessive electron emission from the grid is likely to prevent the grid from performing its proper controlling function.

Such objectionable electron emission from electrodes depends of course upon the temperature the electrode assumes in operation of the tube, and also the nature of its surface as an emitter of electrons at a high temperature level. The heat accumulated by electrodes during operation of a tube is dissipated largely by radiation, assisted by conduction of heat to the outside of the tube envelope through the supporting elements for the electrode; and from the standpoint of temperature rise it is desirable that the electrode should have a surface of good heat radiating qualities. Also, in addition to facilitating radiation of heat from an electrode to reduce its operating temperature, it is desirable hat the surface of the electrode should be such as to provide a minimum of electron emission at such operating temperature.

With these and other considerations in mind, the primary object of this invention is to provide a surface coating for electrodes of electron discharge tubes which will facilitate heat radiation and reduce electron emission at the relatively high temperature the electrode may assume, as compared with the plain metallic surface of the electrode. More specifically, this invention involves the formation of a coating or layer of a sulphate of chromium on the surface of the electrode to improve its heat radiating ualities and largely inhibit electron emission.

This application is a continuation-impart of my prior applications Ser. No. 12,726, filed March 3, 1948, and Ser. No. 12,725, filed March 3, 1948 which issued on June 27, 1950 as Patent No. 2,513,255.

This invention may be employed for various types and forms of electrodes for electron discharge tubes, under conditions Where improved heat radiation and reduced electron emissivity are desirable; and typical examples of such electrodes are illustrated in the accompanying drawmgs.

In these drawings, Fig. 1 illustrates the tantalum electrode of the tube of my prior application, Ser. No. 12,726, with which the coating of a sulphate of chromium in accordance with this invention may be used to advantage; and Fig. 2 illustrates the grid of the tube disclosed in my prior application, Ser. No. 12,725, with which this same coating may be used to advantage.

Referring to Fig. 1, the tantalum anode illustrated comprises a circular thin sheet of tantalum with a peripheral flange 21, and radial ribs or corrugations 28 to give this tantalum sheet sufiicient stiffness or rigidity to prevent excessive warping when heated. A pair of brackets 29 of iron or steel are spot welded to the central portion of this anode A at a large number of closely spaced points in accordance with the disclosure of my prior patent, No. 2,456,540, December 14, 1948; and a supporting rod 30 attached to these brackets 29 facilitates supporting and sealing the anode in the tube envelope in the desired manner.

Referrin to Fig. 2, the control grid G herein illustrated comprises a body portion of concentric rings attached at the proper spaced intervals to a pair of cross members Bl. This grid is arranged to be supported at its center and held against sidewise displacement in a manner not material to the present invention, and illustrated and described in detail in my prior application Ser. No. 12,725, filed March 3, 1948.

The electrode coating characteristic of this invention consists essentially of a sulphate of chromium closely bonded to the surface of the electrode, such as the tantalum anode at Fig. 1, or the grid of Fig. 2 made of nickel or other material suitable for convenient fabrication of the parts.

This coating is preferably applied in accordance with the procedure or process described in my prior applications, Ser. No. 12,725 and Ser. No. 12,726 above mentioned, and disclosed and claimed in my copending application Ser. No. 115,103, filed September 10, 1949. It is found that the coating or film of a sulphate of chromium has a coefiicient of heat radiation much higher than the plain metal to which it is applied, and also has the desired low degree electron emissivity at a relatively high temperature.

It should be understood that the particular electrodes illustrated and described merely represent typical applications of the heat radiating and electron emission inhibiting coating characteristic of this inventon, and that this coating may be applied to the various other forms and types of electrodes.

What I claim is:

1. A tantalum anode for electron discharge tubes having a surface coating of a sulphate of chromium to increase its heat radiation and reduce its electron emission.

2. A tantalum anode for electron discharge tubes having baked thereon a coating of chromium sulphate for decreasing electron emission.

3. An electrode for electron discharge tubes comprising, a body of metal capable of emitting electrons at an elevated temperature, and a coating closely bonded to the surface of said metal and consisting essentially of a sulphate of chromium.

4. A control grid for gas tubes comprising, a plurality of spaced grid bars having a uniform coating of a sulphate of chromium to reduce electron emission from the grid for the same operating temperature.

5. An electrode for electron discharge tubes tending to assume a relatively high temperature in the operation of a tube, an electrode comprising a body of a metal capable of emitting electrons at an elevated temperature, and a coating closely bonded to the surface of said metal and consisting essentially of a sulphate of chromium for facilitating radiation of heat from the electrode and reducing electron emission at said relatively high temperature.

EARL K. SMITH.

No references cited.

Claims (1)

1. A TANTALUM ANODE FOR ELECTRON DISCHARGE TUBES HAVING A SURFACE COATING OF A SULPHATE OF CHROMIUM TO INCREASE ITS HEAT RADIATION AND REDUCE ITS ELECTRON EMISSION.

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