US2717975A

US2717975A - Cathodes for electron tubes

Info

Publication number: US2717975A
Application number: US218383A
Authority: US
Inventors: Wihtol Weltis
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-03-30
Filing date: 1951-03-30
Publication date: 1955-09-13
Anticipated expiration: 1972-09-13

Description

Sept. 13, 1955 w w o 2,717,975

CATHODES FOR ELECTRON TUBES Filed March 50 1951 IN VE/VTOR WELT/S W/HTOL BY W R/VEYS United Srtates Patent CATHODES FOR ELECTRQN TUBES Weltis Wihtol, Redwood City, (Ialif.

Application March 30, 1951, Serial No. 218,383

2 Claims. (Cl. 313-631) This invention relates generally to cathodes for electron tubes.

It is a particular object of this invention to provide a self-heated cathode having a particular utility in electron tubes having concentrically arranged electrodes.

It is another object of this invention to provide a cathode for concentrically arranged electrodes which heats very rapidly whereby the cathode heating current may be turned off during standby periods without experiencing the usual long heat-up time.

It is a further object of this invention to provide a self-heated cathode structure for concentrically arranged electron tubes having good mechanical strength and the ability to withstand frequent heatings and coolings without substantial change in the positioning of the various tube elements.

These and other objects of the invention will appear from the following description in connection with the accompanying drawings which illustrate one embodiment of the invention and in which Fig. 1 is a top plan View showing the improved selfheated cathode structure;

Fig. 2 is a detailed longitudinal sectional view substantially on the line 22 of Fig. 1; and

Fig. 3 is a detailed cross-sectional view substantially on the line 33 of Fig. 2.

The invention is illustrated showing only a portion of ,the electron tube in which the self-heated cathode is to be used with all of the remaining elements of the electron tube eliminated for simplicity of understanding.

The improved cathode structure is illustrated in association with the usual re-entrant stem (Fig. 2) of an electron tube. Two laterally spaced cathode supports 11 and a center cathode supporting rod 12 are fused to the stem 10. The center rod 12 is located between the two laterally spaced cathode supports 11 and extends upwardly beyond the upper ends of the outer rods 11, as appears in Fig. 2. The upper ends of cathode supports 11 are displaced inwardly, as appears in Fig. 2.

Means are provided upon the supports 11 and 12 to mount a tubular cathode. These means include a mounting ring 13 and an eyelet 14 spaced apart longitudinally. The mounting ring 13 is arranged coaxially with the center supporting rod 12, and is aflixed to the inwardly displaced upper ends of the rods 11. The eyelet 14 is secured to the upper end of supporting rod 12 and it comprises a cylindrical portion 15, a flange 16 and a cylindrical portion 17. The cylindrical portion is secured 2,717,975 Patented Sept. 13, 1955 ICC to the upper end of supporting rod 12. The outer diameter of the cylindrical portion 17 is the same as the outer diameter of the ring 13.

A tubular cathode 18 is secured to and extends between the cylindrical portion 17 of the eyelet 14 and the ring 13. The cathode is preferably made of thin metal, such as tantalum having a thickness of .0005. It should be proportioned so that its operating temperature is in the range of approximately 1000 Kelvin and it is heated not quite to incandescence.

The cathode supports 11 are used as the cathode lead and one heater lead and the cathode support 12 is used as the other heater lead.

A circular heat shield 19 is secured to the rods 11 to shield the stem 10 from radiation within the tube.

In actual practice it has been found that the cathode of this invention will reach operating temperature in approximately /2 of a second instead of the usual minute. This greatly reduces the standby problems and tends to lengthen tube life.

This application describes the preferred embodiment of this invention and is merely illustrative. This application contemplates such changes as fairly fall within the scope of the appended claims.

I claim:

1. A uniformly heated cylindrical cathode structure for an electron tube having a low noise factor including a first cylindrical support, a second cylindrical support, said first and second cylindrical supports being of the same diameter and arranged coaxially with respect to and longitudinally spaced from one another, a thin metallic self-heated cathode tube less than .001 inch thick having an operating temperature of the order of 1000 Kelvin and being connected to the exterior of and extending between said cylindrical supports, and two heater leads, one lead being connected to said first cylindrical support and the other lead being connected to said second cylindrical support.

2. A uniformly heated cylindrical cathode structure for an electron tube having a low noise factor including a first cylindrical support, a second cylindrical support, said first and second cylindrical supports having the same diameter and being arranged coaxially with respect to and longitudinally spaced from one another, a thin metallic self-heated cathode tube having a thickness of the order of .0005 inch and being connected to the exterior of and extending between said cylindrical supports, and two heater leads, one lead being connected to said first cylindrical support and the other lead being connected to said second cylindrical support.

References Cited in the file of this patent UNZTED STATES PATENTS 1,881,644 Jones Oct. 11, 1932 1,897,229 Bohm Feb. 14, 1932 1,954,203 Gurtler Apr. 10, 1934 2,269,081 Felsner Ian. 6, 1942 2,468,736 Butler May 3, 1949 2,473,550 Spencer June 21, 1949 2,587,169 Kivari Feb. 26, 1952 2,614,942 Loosjes Oct. 21, 1952