US2547200A - Getter structure for electric discharge tubes - Google Patents

Description

April 3, 1951 E. G. DORGELO GETTER STRUCTURE F OR ELECTRIC DISCHARGE TUBES Filed NOV. 22, 1946 FIG.!

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EDUARD G ERARDUS DORGELO AGENT Patented Apr. 3, 1951 GETTER STRUCTURE FOR ELECTRIC DISCHARGE TUBES Eduard Gerardus Dorgelo, Eindhoven, N etherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application November 22, 1946, Serial No. 711,636 In the Netherlands September 15, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires September 15, 1965 .7 Claims.

1 This invention relates to an electric discharge tube, in which the electrons emitted. by the cathode are formed into a beam by means of a suitable electrode system. Such tubes, in which the electrons are formed into a beam, may fulfil very different functions. A very important specimen .of this kind of tube is the cathode-ray tube either comprising a luminescent screen or a number of collecting anodes. The first-mentioned tubes are used for taking oscillogramsand for television purposes. The last-mentioned group of tubes comprises inter alia deflection tubes which are used for amplification instead of normal gridamplification tubes. Recently another kind of tube, in which use is made of electron streams formed into beams, has become very important viz. tubes incorporating so-called cavity resonators. influence somehow electrical oscillations, more particularly high-frequency oscillations.

As a rule discharge tubes of the aforesaid kind are highly exhausted. Sometimes, use is still made of tubes having a gasfilling. In both kinds of tubes the annoying phenomenon is inherent that ions either originating from the gasfilling or left after exhaustion, travel in a direction opposite to that of the electrons and finally reach the cathode. The cathode is not capable of withstanding them, so that particularly the cathode centre breaks down after a given number of working hours. Consequently, the useful life of the tube is reduced by the ion bombardment.

For cathode ray tubes measures have already been proposed to avoid the aforesaid drawback. To such end the cathode was made annular so that the ion stream is no longer capable of impinging on the cathode, but traverses the aperture of the cathode and finds its way to the part of the tube behind the cathode. Though such a construction constitutes a considerable progress, it still has the drawback that the ions are not actually made inoffensive, in that they can always be influenced again by the electrode system and continue to exert their detrimental efiect in the tube.

An electric discharge tube according to the present invention comprises an electrode system at least consisting of a cathode and means for forming into a beam the electrons emitted by this cathode, the cathode having an aperture through which the ions travelling in a direction opposite to that of the electrons in the beam, are capable of traversing the cathode without hitting the emitting surface, this tube beingcharacterized in that an ion getter is provided behind the aperture of the cathode.

These tubes serve to produce, amplify or By placing an ion getter behind a perforated cathode any ions traversing the cathode are collected and made inoiiensive. Consequently, the ions can no longer partake in the cycle in the tube and consequently can no longer cause annoying phenomena.

Naturally, the getter in gasfilled tubes requires to be such that only ions of detrimental gas moleculesare captured. A very suitable ion getter is zirconium which is provided, for instance in the form of a plate or spiral, behind the cathode.

The temperature of the ion getter afiects to a certain extent its capacity of capturing ions. According to one particular form of construction of the invention the ion getter can be heated. This can take place either by means of a particular heating element or by a heat conducting junction of the getter to the cathode of the tube.

0 In the last-mentioned form of construction the ion getter and the cathode may form a structural assembly.

Another means for heating the getter to the required temperature consists in designing and proportiom'ng it in such manner that the ion bombardment yields the required heating.

In order that the invention may be clearly" understoodand readily carriedinto effect it will now be explained more fully with reference to the accompanying drawing, in which oneform of construction of a cathode for a tube according thereto, wherein the ion getter and the cathode structurally form an assembly, is represented diagrammatically.

Fig. 1 is a longitudinal sectional view of a discharge tube showing an ion getter of plate form; and

Fig. 2 is a similar view with an ion spiral form.

In Fig. 1 of the drawings, the reference numeral I denotes a circular heating helix for the annularly arranged emitting material 2. The emitting material 2 is provided on a round casing 3 having a central aperture 4. Behind this aperture is provided a zirconium plate 5 which is secured to the casing 3 at 6. In this form of getter of construction the temperature of the plate 5 will" trode system comprising a cathode provided with i an emissive surface and means for forming into a beam the electrons emitted from said surface, said cathode having an aperture through which ions travelling in a direction opposite to that of the electrons in the beam are capable of traversing the cathode without striking the emissive surface, a rigid structural support for said cathode, and an ion getter member mounted rigidly on the support and disposed behind said aperture.

3. An electron discharge tube, as set forth in claim 2, in which said ion getter member is constituted by a zirconium plate.

4. An electron discharge tube, as set forth in claim 2, wherein said ion getter member is heated through conduction from said cathode.

5. An electron discharge tube, as set forth in claim 2, wherein said ion getter member is thermally connected to said cathode structure.

6. An electron discharge tube having an electrode system comprising a cathode provided with an emissive surface and means for forming into a beam the electrons emitted from said surface, said cathode having an aperture through which ions travelling in a, direction opposite to that of the electrons in the beam are capable of traversing the cathode without striking the emissive sur face,a rigid structural support for said cathode,

and an ion getter member mounted rigidly on the support and disposed behind said aperture, said member being constituted by a zirconium helix.

7. An electron discharge tube comprising at east a cathode element and an anode, with the cathode element embodying a heating element, an encircling shell, a cathodic surface on the shell with said surface and the shell being formed to have an aperture through which positive ions may pass without striking the cathodic surface, 7

and an ion getter secured to the shell and disposed behind the aperture in the cathodic surface and the shell.

EDUARD GERARDUS DORGELO.

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

UNITED STATES PATENTS Number Name Date 1,632,080 Johnson June 14, 1927 1,859,043 Maartens May 17, 1932 1,991,279 Holst Feb. 12, 1935 2,038,341 Bruche Apr. 21, 1936 FOREIGN PATENTS Number Country Date 297,332 Great Britain Sept. 17, 1928

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