US2682619A

US2682619A - Cold cathode gas discharge tube

Info

Publication number: US2682619A
Application number: US45067A
Authority: US
Inventors: Leo R Landrey
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1948-08-19
Filing date: 1948-08-19
Publication date: 1954-06-29
Anticipated expiration: 1971-06-29

Description

J1me 1954 L. R. LANDREY 8 COLD CATHODE GAS DISCHARGE TUBE Filed Aug. 19. 1948 l /7\ /7 E I F I W a 'r- INVENTOR. 26 BYLeo RJJ aHdPey Attorney Patented June 29, 1954 COLD CATHODE GAS DISCHARGE TUBE Leo R. Landrey, Lynbrook, N. Y., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application August 19, 1948, Serial No. 45,067

8 Claims. 1

The present invention relates to gas filled discharge devices, and more particularly to gas discharge tubes having a cold cathode.

An object of the present invention is the provision of a cold cathode gas filled discharge tube, having substantially no variation in firing characteristics between successive tests.

Another object of the present invention is the provision of a gas discharge tube having a high degree of stability.

A further object of the present invention is the provision of a cold cathode gas filled discharge tube having a more uniform field distribution between the electrodes whereby a more predictable discharge characteristic is obtained.

Still another object of the present invention is the provision of means within a gas discharge tube for assisting the initiation of the electric discharge within the tube, and for decreasing ionization time. I

Still another object of the present invention is the improvement of the electrical characteristics of a cold cathode gas discharge device.

The foregoing objects, and others which may appear from the following detailed description are obtained by providing within a gas filled envelope a rod-like cathode, a semi-cylindrical anode having its convex surface facing the cathode, and an ionization producing strip of metal near the discharge region within the tube but still not directly in the discharge region.

In a preferred form of the present invention the semi-cylindrical anode is provided with an aperture therein at a point intermediate its ends. A getter capsule is secured to'the anode on the concave side thereof with the discharge aper-.

ture of the capsule in line with the aperture in the anode. Thus, as the getter is flashed during the processing of the tube, the active material from within the getter capsule is sprayed through the aperture in the anode to strike the cathode rod, and thereby activate the rod. Some of the getter material, which does not strike the cathode rod, is deposited on the interior wall of the envelope and serves as a clean-up material for undesired gases within the tube.

The present invention is particularly directed to a further improvement of a gas discharge tube of the type disclosed in an earlier filed application by Gerald C. Rich, Serial No. 39,391 filed July 19, 1948, titled Cold Cathode Gas-Filled Diode, and assigned to the assignee of the present application.

The present invention will be more clearly understood by reference to the following detailed description, which is accompanied by a drawing in which Fig. 1 illustrates in an enlarged elevational view, an embodiment of the present invention, while Fig. 2 illustrates a transverse cross sectional view taken along line 22 of Fig. 1.

The gas discharge tube shown in Fig. l includes a sealed envelope 10, preferably of a vitreous material, filled with ionizable gas at a reduced pressure. Various gases may be used, argon and/or neon being typical examples of gases which may be used. The discharge structure within the envelope includes a rod-like cathode |2 and an apertured semi-cylindrical anode Hi. The semi-cylindrical anode I4 is provided with wings l6 and I8 along the opposite vertical edges. To the wings l6 and I8 are attached support rods 20 which pass through insulating

spacers

22 and 24, and serve to support the anode l4 and maintain it in its desired position within glass envelope Hi. The cathode I2 is a solid rod, which passes through apertures in the

insulating spacers

22 and 24 to hold it in its proper.

position within the glass envelope l0, and in the proper spatial relationship with anode M. The support rods 20, and the cathode l2 are provided with conductive extensions passing through the header 26 at the base of the tube to form lead in wires 28. Anode I4 is provided at substantially its mid-point with an aperture 15. Aperture 15 may be provided by dividing anode 14 into two parts spaced apart at the center. Immediately in back of aperture or gap 15, between the two parts of the anode, and secured to the support rods 20 by means of a getter supporting plate I! is a getter capsule ll. Alternatively, it may be secured directly to the concave surface of anode M. The getter capsule is in the form of a hollow iron sleeve filled with a getter material such as barium or other alkaline earth metal. The capsule H is provided with a small aperture IS on the side facing anode l4, that is, away from the supporting plate I1, and directly in line with the aperture in anode l4.

At one stage of the processing of the tube, plate I! is heated by means of induction coils. Heat developed in plate l1, going to the getter capsule Il", causes the alkaline earth metal with in the capsule to be vaporized and to spray out of aperture l9. Some of the vaporized material is deposited on cathode rod 12 where it thereafter serves as an activating material for the cathode. Another portion of the vaporized metal is deposited on the inner wall of glass envelope l0 where it serves in a known manner to clean up undesirable gases within the tube. The restricted size of area between the two parts of anode l4 insures that the gettering and activating material from the capsule ll will be deposited only on the central portion of the cathode rod l2, and on only an adjacent portion of the interior wall of the envelope [0. None of the activating material will be deposited on the

insulating spacers

22 and 24, thus preserving a high insulation value between the cathode and the anode.

Due to the semi-cylindrical form of the anode 14 with the convex surface facing the cathode 12, the actual discharge region within the tube is restricted to a comparatively narrow zone. Thus, the voltage breakdown characteristics of the tube are maintained more nearly uniform than has been the case in previously known tubes of which I am aware.

In order to help initiate the discharge and decrease ionization time, without affecting the electrode spacing in the discharge region, I provide a small strip of radium impregnated ma? terial 3i! welded to one of side Wings 18 of the anode. I have found that in some tubes actually built and tested, the presence of a radium impregnated strip 39, with about two micrograms of radium in the strip, caused the breakdown voltage within the tube to be stabilized within more narrow limits than previously possible.

The time required for ionization and breakdown to take place was found to be maintained within very close limits during the life of the tube. Though some of the tubes actually built and tested used a nickel cathode rod and a barium metal within the getter capsule ll, it is contemplated as being within the scope of the present invention to use a molybdenum rod for the cathode l2 and a barium-telluride mixture within the getter capsule ll.

While I have shown and particularly described an embodiment of the present invention, it should be clearly understood that my invention is not limited thereto, but that modifications within the scope of the invention may be made.

What is claimed is:

l. A gas discharge tube having, within a hermetically sealed casing, a rod-like cathode, a semi-cylindrical anode having a central aperture therein, the convex surface of said anode facing said cathode, a getter capsule supported in spaced relation with the side of said anode remote from said cathode, said capsule having an aperture therein aligned with the aperture in said anode, and an ancillary strip of metal having ionization producing properties supported on said anode in a region remote from the region of closest approach between said semi-cylindrical anode and said cathode.

2. A gas discharge tube including a hermetically sealed casing containing an ionizable gas, a number of electrodes within said casing, said electrodes including an elongated cathode, a semi-cylindrical anode having a central aperture along one side, the convex surface of said anode facing said cathode, a getter capsule supported in spaced relation with the side of said anode remote from said cathode, said capsule havingan aperture therein aligned with the aperture in said anode, said anode having a number of diametrally disposed wing-like extensions thereon, at least one of said wing-like extensions supporting an ionization producing strip of metal.

3. A gas discharge tube having, within a hermetically sealed casing, a rod-like cathode, and a semi-cylindrical anode having a central aperture therein, the convex surface of said anode facing said cathode, a getter capsule supported in spaced relation with the side of said anode remote from said cathode, said capsule having an aperture therein aligned with the aperture in said anode.

4. A gas discharge tube including a hermetically sealed casing containing an ionizable gas, and a number of electrodes within said casing, said electrodes including an elongated cathode, a semi-cylindrical anode having a central aperture along one side, the convex surface of said anode facing said cathode, a getter capsule supported in spaced relation with the side of said anode remote from said cathode, said capsule having an aperture therein aligned with the aperture in said anode.

5. A gas discharge tube including a hermetically sealed casing containing an ionizable gas, and a number of electrodes within said casing, said electrodes including an elongated cathode, and a semi-cylindrical anode having a central aperture along one side, the convex surface of said anode facing said cathode, a getter capsule supported on the side of said anode remote from said cathode and spaced from said aperture, said capsule having an aperture therein aligned with the aperture in said anode, said anode having a number of diametrally disposed wing-like extensions thereon and anode supporting rods secured to the side of said extensions remote from said cathode.

6. A gas discharge tube having, within a hermetically sealed casing, an elongated cathode, and a semi-cylindrical anode having its axis parallel to said cathode, the convex surface of said anode facing said cathode, an electron emissive material on said cathode, and an ancillary strip of metal having ionization producing properties supported on said anode in a region remote from the region of closest approach between said semicylindrical anode and said cathode.

'7. A gas discharge tube including 2. hermetically sealed casing containing an ionizable gas, and a number of electrodes within said casing, said electrodes including an elongated cathode, a semi-cylindrical anode having its axis parallel to said cathode, an electron emissive material on said cathode, the convex surface of said anode facing said cathode, said anode having a number of diametrally disposed wing-like extensions thereon and anode supporting rods secured to said extensions.

8. A gas discharge tube including a hermetically sealed casing containing an ionizable gas, and a number of electrodes within said casing, said electrodes including an elongated cathode, a semi-cylindrical anode having its axis parallel to said cathode, an electron emissive material on said cathode, the convex surface of said anode facing said cathode, said anode having a number of diametrally disposed wing-like extensions thereon, at least one of said wing-like extensions supportingan ionization producing strip of metal.

References Cited in the file of this patent UNITED sTATEs PATENTS Number Name Date 1,531,301 Metzger Mar. 31, 1925 1,658,568 Moore Feb. 7, 1928 1,964,506 De Boer et a1 June 26, 1934 1,990,041 Loewe June 12, 1930