US1914762A - Cathode glow discharge device - Google Patents

Description

Jun 20, 1933. c THOMAS 1,914,762

CATHODE GLOW DISCHARGE DEVICE Filed Sept. 11, 1950 ATTORNEY lamps yp Patented June 20, 1933 UNITED STATES PATENT OFFICE CHARLES HASTINGS THOMAS, 0F BLOOMFIELI), NEW JERSEY, ASSIGNOR TO WESTING- HOUSE LAMP COMPANY, A. CORPORATION OF PENNSYLVANIA on'rnonn GLOW nrsonanen nnvrcn Application filed September 11, 1930. Serial No. 481,181.

This invention relates to gaseous conduction devices and more particularly to gaseous conduction devices utilizing the cathode glow as a source of illumination. More particularly this invention relates to negative glow employing electrodes of the crater One of the objects of the present invention is to provide an improved crater type electrode for cathode glow discharge devices.

Another ob'ect of this invention is to provide a simplified electrode assembly for crater lamp devices.

Another object of this invention is to provide a simple eificient cathode glowdlscharge device of the crater lamp type, having a relatively low breakdown potential.

Another object of this invention is to provide an improved type television lamp.

In accordance with the ObJGCtS of the present invention I have devised a novel type of crater electrode and a novel electrode assembly in constructing a cathode glow discharge device having a relatively low breakdown potential as compared to devices heretofore devised.

Before further disclosing the nature and scope of the present invention reference should be made to the accompanying drawing wherein Fig. 1 is a side elevational view partly in cross section of a cathode glow dlscharge de- Wice constructed in accordance with the present invention;

Fig. 2 is a view of the anode electrode taken along plane IIII 1;

Fig. 3 is a cross sectional view taken along plane III-III Fig. 1;

Fig. 4 is an enlarged cross sect onal v1ew of the electrode assembly showing one type of crater electrode;

Fig. 5 is a cross sectional view taken along plane VV Fig.4; I

Fig. 6 is an enlarged cross sectional view of a second modification or type of crater electrode that is useful in the present invention; p

Fig. 7 is a cross sectional view taken along plane VIIVII Fig. 6;

Fig. 8 is a third modification or type of crater electrode which is useful in the present invention;

Fig. 9 is a cross sectional view taken along plane IX-IX Fig. 8; and

Fig. 10 is aside elevational view partly in cross section of a second type of crater electrode which may be modified exteriorly in accordance with the showings in Figs. 4, 6 and 8.

Referring to Fig. 1 a cathode glow dis-. charge device utilizing crater type electrodes constructed in accordance with the present invention is comprised of an enclosing envelope 1, preferably comprised of glass, an inert gas filling, an anode electrode 2 and a crater type electrode 3.

Heretofore in the art crater lamp devices suitable for use in television and the like arts have been constructed. The crater electrode commonly employed has been comprised of a cylindrical metal body the exterior surface "of which has been enclosed in a dielectric insulating sleeve member extending beyond the electrode in such manner as to support and insulate an anode electrode. The anode electrode was substantially a sheet of metal such as nickel, totally closing the end of the insulating sleeve member.

In order to obtain the pin point of light essential for its use as a television lamp, for example, the anode electrode was perforated at one point to permit the enclosed cathode glow discharge of the crater electrode to be visible. Ineffect the prior art device enclosed the crater electrode within a light impervious refractory cylinder both ends of which were closed, one end by the cathode electrode and the other end by the anode electrode and the luminescence of thecathode glow discharge was permitted to escape from the enclosure through a perforation in the anode electrode.

Such an electrode structure and assembly has many commercial and manufacturing disadvantages. It is diiiicult to assemble andit is difficult to thoroughly degasify the enclosed metal and refractory material elements so that a steady and constant type of negative glow discharge may be maintained within the device during operation. Such.

devices heretofore devised have been characterized by relatively high breakdown potentials of the orderof 200 to 300 volts.

By the practice of the present invention I 5 have materially simplified the electrode assembly by proyiding a new type of crater electrode, a new t e of anode electrode and method of assemb ing the same, whereby the breakdown potential of the device has been reduced to approximately 100 volts or less depending upon the electrode spacing, electrode composition, gas pressure, gas compos1- tion, and the like factors.

The new type of crater electrode of the present invention is comprised of an open ended hollow metal body constructed in accordance with the teachings of my copending application Ser. No. 41 ,091 filed December 28, 1929 which application is assigned to the same assignee as the resent invention. In this copending application I disclose this type of electrode in the manufacture of discharge devices of the positive column type.

When an electrode of this type is employed in discharge devices wherein the lumines-v cence of a cathode glow discharge only is desired, it is highly essential that the cathode glow be confined within the recessed portion of the electrode. At relatively low potentials the cathode glow discharge appears to concentrate within the recessed portion of this type of electrode, but at higher voltages there is a tendency for a slight glow to distribute itself about the exterior surface of the electrode. This creeping of the glow about the exterior surface of the crater electrode may be eliminated by exteriorly surfacing the electrode with dielectric materials such 40 as refractory metal oxides, dielectric glasses or similar vitreous materials or by means of an exterior close fitting metal sleeve member comprised of metals having a higher cathode drop in potential than the specific metal comprising the crater type electrode.

These modifications in the crater type electrode useful in the present invention have been set forth in Figs. 4, 6 and 8. In Fig. 4, for example, the exterior surface 4 comprises 59 a refractory metal oxide, such as aluminium oxide, magnesium oxide, zirconium oxide, thorium oxide and the like, or admixtures of these oxides that may be found useful for the same specific purpose.

These oxides may be applied in any convenient manner, such as by applying the same to the surface of the electrode as an adhesive paste or suspension and baking to consolidate. For best results the refractory CO metal oxides should make intimate and close contact with the exterior surface of the electrode.

The second modification illustrated in Fig.

-6 is an enclosing dielectric sleeve member (3 such as glass or similar vitreous material.

This sleeve member should also be relatively close fittin andmay be retained in position about the e ectrode b any convenient means, such as pinch 5 as i ustrated.

The third modification contemplated within the scope of the present invention comprises an exterior metal sleeve member comprised ofmetal of higher cathode dropin potential than the specific metal comprising the electrode illustrated in Fig. 8, which also is preferably close fitting to the exterior surface of the electrode and may be welded or otherwise electrically connected to the leadmg in su port wire as shown at 6 in Fig. 8.

Depen ing upon the use and application of the crater principle in the specific device constructed, the recessed ortion of the electrode may be compris of a cylindrical openin or a conical shaped opening as illustrated in Fig. 10.

Depending also upon the desired application and electrical characteristics of the device the crater electrode may be comprised of different electrically conductive materials heretofore found useful for the purpose, but for the purposes of greater operating efficiency and lower break down voltage I preferably employ thermionically active material, such as misch metal, thorium or other rare refractory materials. I may also employ alloys of these metals or I may employ an electrically conductive material shaped in the manner shown, the interior surface of the recessed portion of the electrode being coated with such themionically active material as may-be suitable for the purposes desired.

The advantages obtained by the use of this type of electrode material upon the operating efficiency and lower breakdown voltage is more fully set forth in copending application above identified.

By so comprising the cathode electrode as above set forth and providing means to retrict the cathode glow discharge to the interior surface of the crater I have found that I l may modify the anode materially so as to simplify the mounting and assembly of the device. The specific modification I employ is illustrated more particularly in Fig. 2 iyhich is a view taken along plane IIII As shown the anode electrode is comprised of a ring or eyelet of electrically conductive material, such as nickel, iron or other suitable material. the diameter of the opening 7 of the eyelet being adjusted so as to give the desired beam of light from the crater or cathode 3.

It is apparent that instead of a ring a perforated sheet may still be employed if desired but other means of mounting must be employed in order to obtain rigidity and reten tion of the same in mounted position so that the desired spaced relationship of anode to cathode is not lost. The specific size and shape of the anode would depend upon the ICS contemplated use and application ofthe device. In the present illustration the ring anode is shown as the preferred embodiment as it is the most readily applied commercial type.

Inthe type of construction indicated the wire comprising the anode electrode may be of such diameter that it may not be distorted through shock and vibration from its mount ed position andthe spaced relationship of the electrodes can be maintained relatively constant overa reasonably long operating life.

The inert gas filling of the crater lamp device may comprise any' of the monatomic gases singly or in combination with proportions of other gases. The pressure of such gas filling employed is dependent upon the desired electrical characteristics of the device. F or example, neon or an admixture of gases comprised of 99.5% neon and .5 argon maybe employed atpressures ranging from approximately to approximately mm. of mercury, depending upon the specific break down voltage desired in the device and also depending upon the specific size and depth of recessed portion of the cathode, and spacing of electrodes.

As a specific embodiment of the present invention crater electrode 3 is comprised at least in part of one of the metals of the rare earth or rare refractory metals, such as misch metal or thorium, the diameter and depth of the recessed portion would-depend primarily on the purpose for which the lamp is ultimately intended and would depend also upon the specific gas or gas pressures employed.

As an illustration the crater electrode may be comprised of one-half inch cylindrical misch metal or thorium body having a diameter of-approximately 150 mils.

With a gas pressurepf 20 to 40 mm. of neon or neon-argon admixture as above identified, a 76 mil cylindrical crater one-quarter inch deep or a conical crater as illustrated in Fig.

" 10 having a base diameter of 110 mil and an altitude of one-quarter inch may be employed to obtain comparable results. I may also employ an electrode of such diameter as to permit me to shape a conical crater having a base diameter of approximately 120 mils and a depth of about five-sixteenths inch with equally good results.

The specific type of electrode opening employed and the size and depth thereof, will depend upon the intrinsic brilliancy desired, which will depend materially upon the contemplated use of the device.

The exterior surface of the cathode is preferably covered with a metallic sleeve member of higher cathode drop in potential than the misch metal or thorium, comprising the main body of the electrode and is preferably comprised of thin sheet nickel shaped as a cylinder of a diameter sufficient to form close contact with the exterior surface-of the electrode and welded thereto in the manner shown and illustrated in Fig. 8.

With such type electrode anode 2 is comprised of a nickel wire of approximately mil diameter shaped in aring as shown in, Fig. 2 the overall diameter of the anode being slightly greater than the diameter of the cathode. The electrodes may be assembled upon leading in support wires 10 and 11 in the manner shown in Fig. 1, or in any other convenient manner, depending upon the contemplated use of the device and a suitable getter may be mounted upon tab 8 supported upon one of the support wires 11 and positioned so that on flashing, to effect purification of the inert gaseous filling, the vaporized material would be deposited upon the enclosing envelope 1 at a point remote from that portion of the envelope which it is desired to maintain transparent.

The electrodes may be mounted upon leading in support wires extending through a stem of the tipless type, if desired.

Having broadly and specifically set forth in the nature and scope of the present invention it is apparent that there may be many modifications and departures made in the cathode glow discharge device disclosed herein and such modifications and departures are anticipated as may fall Within the scope of the following claims:

lVhat is claimed is:

1. A cathode for a cathode glow discharge device comprised of thorium, one face of said thorium cathode being recessed an appreciable depth and the remaining faces being sur faced with glow discharge suppressing sheathing material.

2, A cathode for a cathode glow discharge device comprising an open ended hollow thorium metal body exteriorly sheathed with dielectric insulating material.

3. A cathode for a cathode glow discharge device comprising an open ended hollow thorium metal body ext-eriorly sheathed with material of relatively higher electrode drop in potential.

4. A gaseous discharge device of the cathode glow type incorporating an inert gas filling, an anode and a cathode of the crater type, said anode electrode comprising a ring shaped metal body positioned in spaced relation to the crater opening of said cathode and said crated electrode being comprised of a metal of relatively low cathode drop in potential exteriorly surfaced with glow suppressing material.

5. A gaseous discharge device of the cathode glow type incorporating an inert gas filling,

an anode and a cathode of the crater type,

said anode electrode comprising a ring shaped metal body positioned in spaced relation to the crater opening of said cathode and said crater electrode being comprised of a metal of relatively low cathode drop in potential exteriorly surfaced with material of relatively high electrode drop in potential.

6. A gaseous discharge device of the cathode glow type incorporatin an inert gas filling, an anode and a cathodi of the crater type, said anode electrode comprising a disc shaped metal body positioned -in spaced relation to the crater opening of said cathode and said crater electrode bein comprised of a metal of relatively low cat ode drop in potential exteriorly surfaced with nickel.

In testimony whereof, I have hereunto subscribed my name this 9th day of September 1930.

CHARLES HASTINGS THOMAS.

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