US2129005A

US2129005A - Braun tube

Info

Publication number: US2129005A
Application number: US717296A
Authority: US
Inventors: Hudec Erich
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-04-08
Filing date: 1934-03-26
Publication date: 1938-09-06
Anticipated expiration: 1955-09-06
Also published as: NL41266C; GB438117A; FR770924A

Description

' sept. 6, 193s. V E. HUDEC 2,125,065

BRAUN TUBEl Filed March 2e, 1954 Patented Sept. 6, 1938 PATENT FFiCE BRAUN TUBE Erich Hudec,

Application March 26,

Berlin, Germany 1934,r Serial No. 717,296

In Germany April 8, 1933 Claims.

' It is well known to apply Braun tubes to the purposes of television by producing between the anode and the deecting plates a rejection chamber which is closed against the deflection space by a diaphragm with an opening of, the diameter of the cathode ray, and in which the cathode ray is defiected by electro-static or magnetic iields in jsuch manner that neither the ray itself nor diffused stray electrons are able to enter the defleclO tion space and in that way to reach the screen of the Braun tube. The fields within the rejection chamber are either Zero so that the cathode ray is allowed to pass unexerted through the diaphragm or they possess such a value that the cathode ray is completely stopped. With this arrangement it is therefore only possible to produce black-white pictures, while the grey intensity Values can not at all be reproduced.

In the art of television it is however indispensable to reproduce all half-tone values of the picture. This may be accomplished in principal fashion by Varying the potential of. a grid electrode arranged near the cathode (e. g. a Wehnelt cylinder surrounding the cathode). In all practical experiments which have been undergone up to now it has been stated that besides a desired variation of the intensity of the fluorescent image point an undesired variation of the position of the point takes place by which the television image is very strongly distorted.

The invention is based on the theory that the variation in the position of the image point is stipulated by asymmetry. In case the heater element is lying not exactly on the axis of the Wehnelt cylinder and the anode, the electrons are accelerated in lateral fashion. The degree of the lateral deflection is determined by the geometrical dimension and by the voltages between the Wehnelt cylinder and the cathode. Upon varying this voltage for the variation of light intensity of the fluorescent point the acceleration of the electrons is Varied, the electrons are lightening the screen in another spot.

The disturbing shifting the image point in the 45 case of Braun tubes with intensity control according to the invention is removed by supporting all electrodes by the aid of a precise gauge, which afterwards upon fixing the electrodes by melting them to the supports may easily be removed 50 without damaging the electrodes.

One object of theinvention is a Braun tube for television purposes comprising a thermionic cathode, a control electrode arranged in the proximity of said cathode, and an anode arranged in operative relationship to said cathode, and

(Cl. Z50-27.5)

wherein the emissive surface of said cathode is exactly aligned with the axis of said control electrode and with the axis of said anode.

A further object of the present invention is a simple method for producing Braun tubes of this kind. Still further objects of. the invention will be seen from the following description.

The invention may be more fully understood with reference to the accompanying drawing in which Fig. 1 shows by way of example an arrangement Vfor mounting the electrodes of the Braun tube in precisely centered fashion, and Fig. 2 shows an exemplary form of a gauge.

In Fig. l, l is the heater element for instance a filament which is sup-ported by two leads which are melted to the press l. All the other electrodes, the Wehnelt cylinder 2, and anode 3 and the

deflection plates

4 and 5 are fastened to two glass rods 6 which are melted with the press i and serve as a support.

As basic element of the gauge according to the Fig. 2 a cylindrical rod 8 is provided which is either guided by two electrodes or better in a special rack independent of the assemblage of electrodes. On this centering rod there are arranged distance pieces 9, I D, l l by which pieces an exactly symmetrical position of the several electrodes is guaranteed. After the several electrcdes having been melted to the glass rods the centering rod and the distance pieces are carefully removed. In order to avoid a damage of the structure the distance pieces may be constructed of two parts and allowed to be opened.

By tensioning the gauge in a frame, which is mounted between two points, it is possible, after removal of the gauge, to examine mechanically whether the electrodes are still exactly centered. For this purpose the gauge frame is rotated between the two points, and a check taken whether the rotary members still run, Since the eye responds very well to slight knocking on the part of rotary members, the accuracy of this test is very considerable.

In carrying out this method it has been found that the single electrodes, which were centered in the gauge with considerable exactitude, did not run cleanly after the removal of the gauge, and required slight subsequent adjustment.

The distortion of the electrodes is due to stresses in the glass. To diminish these stresses the two glass rods, after al1 electrodes had been fused in, were again .greatly heated over their entire length and then slowly cooled. The stresses, however,Y were not in this way eliminated.

The invention is based on the recognition that the stresses in the glass are due to the extensive heating of the metallic attachment wires of the electrodes. These wires require to be greatly heated when fused into the glass rods. After cooling the wires contract, and produce the undesirable stresses. Subsequent heating of the holding rods is of little value, as in this way the attachment wires are also heated and contact anew when allowed to cool.

The objections associated with the known method are avoided according to the invention by fitting on the electrodes short glass rods, which are fused to the holding rods. The advantage of this method consists in the fact that when fusing glass to glass a considerably smaller heating is required, and that the glass may be heated locally, whereas otherwise the metallic connecting wires are also heated over their entire length and contract over their entire length when allowed to cool.

To the electrodes, for the purpose of their attachment, there are Welded merely Very short metallic rods composed of a suitable fusing wire, and on to these there are fused short thin glass rods. The electrodes are then assembled in the gauge, and finally the holding rods are fused to the glass rods. Preferably at first the outermost deflecting plate is fused to the glass rods, so that the same is furnished with a hold and is unable to flex.

In order that the fusing of the glass rods may take place as quickly as possible and the gauge not heated excessively, it is desirable to employ a glass having the lowest possible fusing point, for example lead glass.

I claim:

l. A Braun tube for television purposes comprising a pinch, two insulating rods secured to said pinch, a thermionic cathode having an emissive surface and being secured to said pinch, a control electrode, and an anode arranged in operative relationship to said cathode, said control electrode and said anode being each secured to, and located in exact axial alignment with respect to said emissive surface by, said two insulating rods.

2. A Braun tube for television purposes comprising a pinch, two glass rods secured to said pinch, a thermionic cathode having an emissive surface and being secured to said pinch, a control electrode, and an anode arranged in operative relationship to said cathode, said control electrode and said anode being each secured to, and located in exact axial alignment with respect to said emissive surface by, said two glass rods.

V3. A Braun tube for television purposes comprising a pinch, two insulating rods secured to said pinch, a thermionic cathode having an emissive surface and being secured to said pinch, a control electrode, an anode arranged in operative relationship to said cathode, and a deflecting electrodes system, said control electrode, said anode, and said deflecting electrodes system being each secured to, and located in exact axial alignment with respect to said emissive surface by, said two insulating rods.

4. A Braun tube for television purposes comprising a pinch, glass rods fused to said pinch, a thermionic cathode having an emissive surface and being secured to said pinch, a` control electrode, and an anode arranged in operative relationship to said cathode, at least one short glass rod secured to said control electrode and to said anode, each, said short glass rods being fused to said glass rods fused to said pinch to secure said control electrode and said anode each to said two glass rods fused to said pinch and so to locate said control electrode and said anode in exact' axial alignment with respect to said emissive surface.

5. A Braun tube for television purposes comprising a pinch, glass rods fused to said pinch, a thermionic cathode having an emissive surface and being secured to said pinch, a control electrode, an anode arranged in operative relationship to said cathode, and a deflecting electrodes system, at least one short glass rod secured to said control electrode, to said anode, and to said deflecting electrodes, each, said short glass rods being fused to said glass rods fused to said pinch to secure said control electrodes, said anode, and said deilecting electrodes system each to said two glass rods fused to said pinch and so to locate said control electrode, said anode, and said deflecting electrodes system in exact axial alignment with respect to said emissive surface.

ERICH HUDEC.