US2433813A

US2433813A - Electric discharge tube

Info

Publication number: US2433813A
Application number: US612217A
Authority: US
Inventors: Robert C Hilliard
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1945-08-23
Filing date: 1945-08-23
Publication date: 1947-12-30
Anticipated expiration: 1964-12-30

Description

Dec. 30, 1947. R. c. HILLIARD ELECTRIC DISCHARGE TUBE Filed Aug 23, 1945 Z 7 8 I 2 4 30 Z 5 .2 $52 MM 3 L- 3 b .l I. d n 2 1 .w F H H M I Go J" .1 .m... .4 Ma i I: |...|l F m b 7 9 0 l l 2 9 2 R Fig.

R Y mm m m m mm m a. 6 a M o a Patented Dec. 30, 1947 UNITED STATE S PATENT ()FFICE ELECTRIC DISCHARGE TUBE Application August 23, 1945, Serial No. 612.217

6Claims. 1

This invention relates to gaseous discharge tubes and particularly to those of the type in which the source of electrons is a cathode spot. It may be designed, if desired, so that the short distance between the electrodes makes the tube useful as a rectifier. It may also be used for producing extremely short pulses, and for other purposes.

An object of this invention is to provide a coldcathode, gaseous discharge tube which has relatively easy, cathode-spot formation without the necessity of heating power for th filaments.

Another object of this invention is to provide an electron discharge tube in which the discharge is controlled, without the expenditure of appreciable energy, by the control grids, for producing extremely short pulses and high peak currents.

A feature of this invention is the use of a carbon grid at the anode to help control the electrode to give a sharp cut-off after the discharge stops.

Another feature of this invention is the use of a glass tube heated and sealed to the carbon electrode to support it.

Another feature of this invention is the use of caesium chloride and aluminum in a highly compressed form as a pill."

Another feature of this invention is the use of an annular metal grid over the cathode cup to prevent sputtering of the cathode-emitting material and to act as keep-alive, where necessary, and to start the discharge.

A further feature of this invention is the use of a strap or baille over said nickel grid to keep sputtered material from forming on the anode grid.

Other objects and features of this invention will be explained hereinafter and will be particularly pointed out in the appended claims.

Figure 1 i a perspective view of the cold-cathode gaseous-discharge tube.

Figure 2 is a longitudinal sectional view of said cold-cathode, gaseous-discharge tube enlarged.

Figure 3 is a perspective view of the cathode cup in partial section.

In Figure 1, the anode wire I of tantalum is welded to material suitable for sealing the glass and is sealed into the base of a hollow glass tube 2 which supports the carbon grid 3.

The carbon grid 3 is further supported by a metal strip 4 with metal wires sealed in and supported by the glass sleeves 5. At the cathode, the lead-in wire 6 passes through the insulating ceramic cup I to the cathode cup and pill. The ceramic cup I is covered by a nickel grid 8 to prevent the sputtering of the cathode-emitting material and thus to act as a keep-alive or to 2 start the discharge. The nickel grid has a he 9 in it to allow the action of the spot discharge. The cathode is further protected from sputtering by a baffle III of metal. The unit is insulated by and mounted upon the glass base I I and sealed in a glass envelope filled with helium at a pressure of 7 to 20 millimeters.

In Figure 2, the glass tube I2 is capped by a metal anode cap I3 to which is attached a tantalum wire I4 supported-by and insulated by a glass tube I5, welded to it as in normal tube construction. The wire I4 is separated from the glass tube I5, except at the base, by an air space IE to prevent cracking from heat. The carbon grid II at the anode gives a sharp cut-01f after the discharge stops and is supported not only by the glass tube I5 but also by the metal strip I8 upheld by the metal wires I9 supported in the glass sleeves 20. At the cathode, the caesium chloride and aluminum compressed into a pill 2I provide a cathode spot. This pill 2I of cathode-emitting material rests in and is contacted by a nickel cup 22 to which is attached the lead-in wire 23. A ceramic cup 24 surrounding and insulating the cathode is covered with an annular grid 25 to prevent sputtering of the cathode-emitting material and to act as a keep-alive, where necessary. The hole 26 in the metal grid is covered by a strap 21 which further prevents sputtered material from reaching the carbon grid II. The getter 28 on each side of the glass mounting 29 is attached by a wire 30 to the stem. The entire glass envelope I2 is filled with helium at 7 to 20 millimeters pressure, or any inert gas; helium gas at low pressure may be used to increase the hold-off" factor and to make the response of the device quicker. The glass envelope is fastened with cement 32 to a base from which project the pins 33. i

In sealing the glass and the carbon together at the anode, the carbon is heated to the softenin point of glass and the glass tube then pushed into the carbon electrode. A mandrel is pushed up into the glass tube during this sealing process to keep the tube open. This process may be useful in other places where keeping the glass tube open is not important, and in those cases a mandrel will not be required.

In Figure 3, the cathode pill" 2I is shown resting in the metal cup 22, said metal cup insulated by the ceramic cup 24. Over all of this is the annular metal grid 24 surmounted by the metal baffle 21.

This tube may be used in the usual strobotron circuit and in many other types of circuit. I have 2. In an electric discharge tube, a graphite electrode and a glass support sealed thereto and a lead-in wire sealed through the glass support and extending into, but spaced from, said graphite electrode, said lead-in wire acting as an anode and being composed of tantalum.

3. In an electric discharge tube, a cathode of material capable of forming a cathode spot, an insulating cup for the part of said cathode away from the discharge, an annular metal cover for the part of said cathode facing the discharge, and a metal shield spaced from but in register with the center of said annulus.

4. In an electric discharge tube, a cathode of material capable of forming a cathode spot, an insulating cup for the part of said cathode away from the discharge, an annular metal cover for the part of said cathode facing the discharge, said annular ring acting as a control grid for the discharge, and a metal shield. spaced from, but in register with, the center of said annulus.

5. In an electric discharge tube, a cathode of material capable of forming a cathode spot, said material comprised of caesium chloride and aluminum highly compressed, an insulating cup for the part of said cathode away from the discharge, an annular metal cover for the part of said cathode facing the discharge, said annular ring acting as a control grid for the discharge, and a metal shield spaced from but in register with the center of said annulus,

6. In an electric discharge tube, a graphite electrode and a glass support sealed thereto and a lead-in wire anode composed of tantalum, sealed through the glass support and extending into, but spaced from, said graphite electrode and a cathode of material capable of forming a cathode spot, said material comprised of caesium chloride and aluminum highly compressed into a "pill," an insulating cup for the part of said cathode away from the discharge, an annular metal cover for the part of said cathode facing the discharge, and a metal shield spaced from but in register with the center of said annulus.

. ROBERT C. HILHARD.

REFERENCES crrm') The following references are of record in the tile of this patent:

UNITED STATES PATENTS OTHER REFERENCES Fansteel Metallurgical Corporation Publication Processing of Tantalum Anodes and Grids for Transmitting Tubes." (Copy in Division 54.)