US2465256A - Gaseous discharge tube - Google Patents

Description

J. G. W. MULDER GASEOUS DISCHARGE TUBE I arch 22, 1949.

Filed April 29, 1946 FIG.

INVENTOR J. G. W. MULDER FIG.

ATTORNEY.

Patented Mar. 22, 1949 2,465,256 I C E GA-SEOUS DISCHARGE TUBE Johannes Gijsbertus Wilhelm Mulder, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as

trustee Application April 29, 1946, Serial No. 665,662 In Belgium February 8, 1945 Section 1, Public Law 690, August 8, .1946

Patent expires February 8, 1965 6 Claims.

This invention relates to arectifier tube with gas or vapour filling and comprising an incandescent cathode.

Of suchtubes, more particularly of those comprising an activated incandescent cathode, the period, of life is materially reduced because, when the tube is switched in with'cold cathode and full anode voltage, the arc voltage-during the heatingup period of the .cathodeis so high that the incandescent cathode .is readily deteriorated. Under these conditions the risk of arc-back is also abnormally great.

It is already known to switch on the anode voltage automatically only when the cathode has attained a determined temperature or at least has been heated up during a given period of time but since the automatic switches required for this purposemustbe-designed for the full anode current, they are bulkyand expensive.

In the rectifiertube withgas or vapour filling according to the invention the incandescent cathode-is surrounded by ashield, owing to. which the'operating voltage is in practice not higher than it would be in a-largetube with, equal pressure and equal distance.between the electrodes without the shield whilst ini front of the aperture or apertures for the passage ofthe discharge there. is provided in association with the shield an auxiliary electrode by which theoperating voltage. is not increased to any appreciable extent and which is shapedand placed in such manner that withv floating potential of the cathode shield and of the auxiliary electrode the igniting voltage of the tube is higher than the anode voltage. The tubes involved are those whose cathode shield has so little influence on the operating voltage that the latter is at the most 25% higher than the lowest possible operating voltage with equal pressure and equal distance between the electrodes without shield. The auxiliary electrode causes a. considerably smaller increase of the operating voltage, which isin most cases not higher than 1 volt. The term igniting voltage is to be understood to meanthe first igniting voltage of thetube after switchingin. This voltage is in most cases higher than the re-igniting voltage if the tube is operated on alternating current. By suitably biassing the cathode shield and the auxiliary electrode the tube is ignited at the normal igniting voltage. The cathode shield and the auxiliary electrodemaybe connected, for example, in commonpr separately through a large resistance ora rectifier, to the anode. "As an alternative, they may be connected jointly to one :point or separately to two points of a potentiometer interposed between. the anode and the cathode. Since the cathode shield and the auxiliary electrode are traversed by a but ;small current #011157 a small-automatic switch required whichpis not largerthan a telephone relay so that the switch may consequently .beinexpensive and of small size as comparedwwith the automatic switches formerly used in the anode lead.

Tubes are also. known whichrequire an auxi1 iary ignition but :inthis case these are tubes which have a highoperating voltage as a result oiadditional screens :or anode arms.

.Itis very simple to manufacture the auxiliary electrode from wire or band and to form it in thessame' shape as the edge of the discharge apertures and to place it at. a short distance in front of the latter.

In tubes in which the discharge can only emerge from the cathode shield inthe direction remotefromthe anode-the provision of an auxiliary electrode according to the invention is particularly advantageous since-it enhances at the same :-time the-auxiliary-anode action of the cathode shield.

Tubes in. which the main discharge can only emerge from'the. cathode shield in the direction remote from the anode but in which the part of the cathode shield adjoining the anode is pierced with one or more igniting holes have the property of igniting immediately after being switched in. In this case the cold cathode is therefore loaded very heavily.

"Igniting holes are holes provided in the part of the cathode shield adjoining the anode, in such manner that before the ionization of the main discharge *path' takes place the electrons emitted in front of the cathode can reach the immediate vicinity of the anode or anodes where the potential for ionization of the gas-filling is sufficient'topermit the initiation of the main discharge Whilst it is practically impossible that coarser particles, for example of emissive material, hurled away'from the cathode can reach the anode through the auxiliary apertures. The latter have so small a free diameter relatively to that of theapertures for the passage of the main discharge. as to be able to pass but a very small portion of. the maximum operating current of the tube.

It. ahordsparticular. advantages to apply the invention. totubesof. this kind and to provide the auxiliaryelectrode not. only in front of the main discharge apertures but to extend it as far as in front ofthe igniting holes.

The inventionwill now be set out more fully with reference to the accompanying drawing in which 1 shows a tube according .to the invention in vertical section, and M $.Fig. 2 is .a perspective view of a cathode shield and of .an'auxiliary electrode according to the invention.

Figure 3 is schematic-circuit showing the pertiin the direction remote from the anode.

nent electrical connections to the electron tube of the invention.

In the figures, reference numeral 1 designates the wall of the tube and 2 the activated incandescent cathode which is fastened in the wall of the tube with the aid of cathode leads 4, surrounded by ceramic tubes IB, and ferrochrome caps 6. The anodes 3 are fastened in the wall of the tube with the aid of anode leads 5 surrounded by ceramic tubes I0, and ferrochrome caps l. The ceramic tubes I are sealed at H with the wall of the tube. Each of the anodes is surrounded by a gauze screen 8 which is fastened around the ceramic tube [0 with the aid of a sleeve 9. The screen 8 leaves only the front surface of the anode free. A screen I2 having a circular bottom portion is interposed between the anodes. The cathode is surrounded by a cylindrical cathode shield 15, having an oversized cap member I8 secured thereto in a raised position in such manner that the discharge can emerge only from the opening between cap l and cap 18 The cap l8 of the cathode shield has pierced in it two igniting holes I1. The auxiliary electrode provided in front of the main discharge aperture is designated by M and consists of an annular thick wire. In front of the igniting hole are little rings I3, also consisting of thick wire. The rings [3 and the auxiliary electrode l4 are interconnected 4 and connected to the cathode shield by connecting wires IS. The cathode shield is connected to the exterior by means of a leading-in wire 2|. The ferrochrome caps 6 of the cathode leads contain a few mercury drops 20 serving as a supply of vapour-forming material. The tube contains, in addition, an argon filling of a few tenths of mm. mercury pressure and can supply a direct current voltage of 110 volts at a current of amps. If the potential of the cathode shield and of the associated auxiliary electrode is maintained floating the tube does not ignite at the full anode voltage. The cathode shield and the auxiliary electrode are connected to a potentiometer of about 3000 ohms at one-third from the cathode end, for example as shown in Figure 3 wherein a potentiometer has one end connected to the anode 3 and the other end connected to the cathode 2, a tapping 4| approximately one-third from the cathode end being connected to the shield I5 and auxiliary electrode M. The current for the cathode shield starts the flow at a voltage of from 10 to 11 volts. The anode current starts to flow almost simultaneously, the anode voltage then being from 30 to 33 volts. The are voltage amounts to 10 volts.

What I claim is:

1. A gaseous discharge device comprising an electron-emissive cathode, anode means, a shield surrounding said cathode and having an opening therein, said opening facing away from such anode means for the passage of dischar current in the direction remote from said anode means, and auxiliary electrode means mounted in front of said opening.

2. A gaseous discharge device comprising an electron-emissive cathode, anode means, a shield surrounding said cathode and having an opening therein, said opening facing away from said anode means for the passage of discharge current in the direction remote from said anode means, and a wire-formed auxiliary electrode mounted in front of said opening, the shape of said electrode being substantially similar to the periphery of said opening.

3. A gaseous discharge device comprising an electron-emissive cathode, anode means, a shield surrounding said cathode and having an opening and apertures therein, said opening facing away from said anode means for the passage of a major portion of discharge current in the direction remote from said anode means, said apertures facing toward said anode means for the passage of a minor portion of discharge current in the direction towards said anode means, and auxiliary electrode means mounted in front of said opening and said apertures.

4. A gaseous discharge device comprising an electron-emissive cathode, anode means, a cylindrical shield surrounding said cathode, said shield having an oversized cap member secured in raised position to the end of said shield adjoining said anode means, said cap member defining an annular opening with said shield for the passage of discharge current in the direction remote from said anode means, and an annular auxiliary electrode mounted concentric with said shield and in front of said opening.

5. A gaseous discharge device comprising an electron-emissive cathode, anode means, a cylindrical shield surrounding said cathode, said shield having an oversized cap member secured in raised position to the end of said shield adjoining said anode means, said cap member defining an annular opening with said shield for the passage of a major portion of discharge current in the direction remote from said anode means, said cap member having apertures therein for the passage of a minor portion of discharge current in the direction towards said anode means, and an auxiliary electrode having an annular portion mounted concentrically with respect to said shield and in front of said opening and ring portions mounted in front of said apertures.

6. A gaseous discharge device comprising an electron-emissive cathode, a pair of anodes, said cathode and said anodes being symmetrically arranged, a flat screen disposed intermediate said anodes, a cylindrical shield surrounding said cathode, said cylindrical shield having an oversized cap member secured in raised position to the end of said cylindrical shield adjoining said anodes, said cap member defining an annular opening with said shield for the passage of a major portion of discharge current in the direction remote from said anodes, said cap member having apertures therein for the passage of a minor portion of discharge current in the direction towards said anodes, and an auxiliary electrode having an annular portion mounted concentrically with respect to said cylindrical shield and in front of said opening and ring portions mounted in front of said apertures.

JOHANNES GIJSBERTUS WILHELM MULDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,084,750 Von Wedel June 22, 1937. 2,183,918 Mulder Dec. 19, 1939 2,217,185 Smith Oct. 8, 1940 FOREIGN PATENTS Number Country Date 886,842 France July 19, 1943

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