US3143685A - Character display cathode ray tube - Google Patents

Description

Aug- 4, 1964 N. D. GLYPTIS CHARACTER DISPLAY CATHODE-RAY TUBE 5 Sheets-Sheet 1 Original Filed June 7, 1957 JNVENTOR. 2,9902% I\ BY g- 9 N. D. GLYPTIS 3,143,685

CHARACTER DISPLAY CATHODE-RAY TUBE Original Filed June '7, 1957 5 Sheets-Sheet 2 INVENTQR.

mrm Jaw WM Aug. 4, 1964 N. GLYPTIS CHARACTER DIS PLAY CATHODE-RAY TUBE Q 3 Sheets-Sheet 3 Original Filed June 7, 1957 .10. fizzy/$1. mfi; a: aw-w eyi United States Patent M CHARACTER DIEELAY CATHODE RAY TUBE Nicholas D. Glyptis, Multi-Tron Laboratory, Inc, 9361 Derby Lane, Westchester, Iii. Continuation of application Ser. No. 664,195, June 7, 1957. This application July 24, 1961, Ser. No. 127,089 8 Claims. (Cl. 3115-15) This invention relates to an improved cathode-ray tube and particularly to a cathode-ray tube which requires a much lower driving signal than those heretofore in common use.

This application is a continuation of my application Serial No. 664,195, filed June 7, 1957, now abandoned.

This is achieved by providing a cathode-ray tube with a cathode-grid structure which is designed to form the electrons emitted from the cathode into a plurality of discrete beams. This should be contrasted with the usual cathode-ray tube, cathode-grid or electron gun structure in which substantially all of the electrons emitted are formed into a single stream.

One object of the invention is to provide, in a cathoderay tube, an electron source including a cathode having an emissive surface and a grid associated with the emissive surface to form the electrons emitted therefrom into a plurality of discrete beams. Another object is to position the grid immediately adjacent the emissive surface of the cathode so that the voltage difference between the grid and the cathode establishes a widely varying voltage gradient across the emissive surface, controlling the area of the cathode from which electrons are emitted.

A further object is to arrange the grid structure adjacent the emissive surface of the cathode, having alternate solid portions and openings therethrough with the ratio of the width of the solid portions to the spacing therebetween being at least 0.05 and less than 0.5. Still another object is to provide a grid in which the ratio of the spacing between the solid portions to the spacing of the grid from the emissive surface of the cathode is at least 1.8 and less than 20.

A further object is to provide, in a cathode-ray tube a source of electrons including means for forming electrons into a bundle comprising a plurality of discrete electron beams, and means for masking a portion of the bundle of electron beams giving the bundle a desired cross-sectional configuration to provide an image of the character on the screen of the tube.

Another object is to provide a source of electrons including means for producing a plurality of bundles each comprising a plurality of discrete electron beams, and a mask having a plurality of openings therein, each defining a character, with one of the character openings associated with each of the bundles. Still another object is to operate the mask at the grid potential.

Further objects, advantages and features of the present invention will be apparent from the description of the specific embodiments thereof illustrated in the accompanying drawings, in which:

FIGURE 1 is a fragmentary cross-sectional view of a portion of an electron tube embodying the invention together with a semi-schematic showing of the circuit connections of various elements thereof;

FIGURE 2 is an enlarged cross-sectional view of the cathode-grid structure;

FIGURE 3 is a sectional view taken substantially along line 33 of FIGURE 2;

FIGURE 4 is a fragmentary cross-sectional View of a modified form of the invention;

FIGURE 5 is a fragmentary cross-sectional view of a further modification of the invention;

FIGURE 6 is an elevational view of a masking member;

3 ,143,685 Patented Aug. 4, 1964 FIGURE 7 is a diagrammatic illustration of the con trol of the grid over cathode emission;

FIGURE 8 is a fragmentary cross-sectional view of another modification of the invention;

FIGURE 9 is a fragmentary cross-sectional view of a further modification of the invention;

FIGURE 10 is a fragmentary elevational view of a modified grid structure for replacement television tubes; and

FIGURE 11 is a fragmentary elevational View of a modification of FIGURE 10.

While I have herein illustrated and shall describe preferred embodiments of this invention, the invention is not limited to the particular forms shown, it being understood that modifications and changes may be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the accompanying claims.

Turning now to FIGURE 1, a portion of the neck of a cathode-ray tube is indicated at 10, and mounted within the neck is an electron gun indicated generally as 11. The electron gun includes a cathode and control grid structure 12, a second grid 13, accelerating grids 14 and 15 and a focusing element 16. A suitable luminescent coating 17 is applied to the inner surface of the tube face. Representative circuit connections for the elements are depicted in FIGURE 1, in which the cathode 18 is grounded while the control grid 19 is returned to a negative potential on a voltage divider 20. The second grid 13 may have a positive voltage of the order of -500 volts with respect to the cathode. Focus electrode 16 is returned to a movable tap 19:: on the voltage divider, and accelerating electrodes 14 and 15 are connected together, and to the coating 17, at the anode or screen potential, which may be of the order of 800020,000 volts depending on the nature of the particular tube.

A suitable deflection system will, of course, be provided, and may be of either the electrostatic or magnetic type. However, inasmuch as the deflection system forms no part of the present invention, it is not illustrated herein. The invention is not limited to an electrostatic focus tube, but may be used with other types of tubes, as for example, those utilizing magnetic focusing.

Turning now to FIGURE 2, the cathode-grid structure 12 is shown in more detail. The cathode 18 is a cylindrical member closed at one end, with a heating element 25 carried therein. The closed end of the cathode is coated with a suitable electron emissive substance 18a. The control grid 19 includes a grid cup 26 which has a small opening 26a in the closed end thereof. A wire mesh grid structure 27 is mounted on a carrier ring 28 and is inserted in the grid cup with the mesh 27 overlying the opening 26a. Supporting ring 28 has a centrally located opening 28a therein which is preferably slightly larger than the grid cup opening 26a and is in alignment therewith. Carrier ring 23 is held in the grid cup by an annular spacing member 29, which in turn is held in place by a retaining disc 30, preferably of a ceramic insulating material. Retaining disc 30 has a central opening therein which receives the cylindrical cathode 18, supporting it in a desired position with the emissive surface 18a in alignment with the openings 26a and 28a.

The grid mesh 27 is so arranged and so positioned with respect to the emissive surface 18a that it screens the emissive surface from the accelerating potentials applied to the grids and exerts an effect or control over the emission of electrons therefrom. It is believed that this control results from the establishment of a Widely varying voltage gradient across the emissive cathode surface 18a. In other words, the voltage applied between the control grid and the cathode substantially modifies the field established by the voltage between second grid 13 and the cathode.

The controlled varying voltage gradient across the emissive surface 18a of the cathode results in a controlled emission of electrons from the emissive surface and in the formation of a plurality of discrete electron beams, rather than one. single stream. This is illustrated in FIGURE 7 where three conditions of operation are shown. Grid wire 27a has applied thereto a voltage equal to 50% of the cutotf voltage. With this voltage on the grid, electrons are emitted from a portion 18a of the emissive surface and form a beam 32a. Grid wire 27b has applied thereto a voltage of the order of 80% of the cutofif. This voltage modifies the voltage gradient across the emissive surface so that electrons are emitted only from an area 1811", which is smaller than the area 1311', form ing a beam 32b. Grid Ware 27c has applied thereto a voltage of the order of 10% of the cutoff, under which condition electrons are emitted from a relatively large area 18a"','F0rming a beam 320. The electrons, having once been formed into discrete beams in this manner, remain as discrete beams and do not combine to form a single beam. The collection of discrete beams emitted from the cathode surface will be designated herein as a bundle of beams, or simply as a bundle.

It has been found that certain physical relationships between the grid and cathode must be satisfied to establish the illustrated grid control over the emission of electrons from the cathode surface. The spacing factor, Which is defined as the ratio of the center-to-center distance between wires of the grid to the distance from the cathode to the grid,

(where a is the center-to-center distance between wires and d is the distance from cathode to grid), should be between 1.8 and 20. The screening factor, which is defined as the ratio of the grid Wire diameter to the centerto-center spacing of the grid wires,

(where r is the grid wire radius and a is the center-tocenter distance between wires), should be between 0.05 and 0.5.

In a representative cathode-grid structure, the grid is composed of a 0.79 mil wire screen with a 100 x 100 mesh, or 10 mil wire-to-wire spacing and with a grid-tocathode spacing of 4 mils. In this structure the spacing factor is 2.00 and the screening factor is 0.079. The grid opening 26a should be no larger than 30 mils for satisfactory spot size, providing nine discrete beams.

The novel cathode-ray tube with the cathode-grid structure which has been discussed can be operated with an input signal much smaller in magnitude than that required by a conventional'cathode-ray tube. For eXample, a cathode-ray tube which required from 5070 volts of signal on the control grid to provide a full range from black to White was modified by the substitution of the specified cathode-grid structure, providing multiple beam operation. The opening 26a in the grid cup has a size suflicient to pass nine separate beams. The modified tube requires a signal of only 5-7 volts for full range operation. As a practical example of the benefit of this improved operation, a television receiver utilizing the novel cathode-ray tube disclosed herein may be operated without the need for a video power amplifier. In fact in some cases, the video signal derived from the second detector is sufficient in and of itself, without further amplification, to provide a full range of contrast in the picture.

A cathode-ray tube having a multiple beam electron source may be used for replacement in a conventional television receiver, i.e. one with a video power amplifier stage. In this case, as shown in FIGURE 10, the opening 26a in the grid cup is 30 mils in diameter and the grid itself comprises two wires 33 in a cross-hair arrangement. The electrons are formed into four discrete beams. As shown in FIGURE 11, the grid cup opening 26a may be square rather than round. Furthermore, only a single wire grid may be used to form the electrons into two discrete beams. This tube has a transconductance increase by a factor of 3, and permits an increase in the operating brightness level of the tube, without a defocussing effect and has a full range of shade, including black, even at high brightness levels.

Turning now to' FIGURES 4, 5 and 6, a modification of the novel cathode-ray tube which is particularly adapted for the projection of characters or symbols, as

"letters, numbers, punctuation or the like on the tube face, is shown. The structure of FIGURES 4 and 5 is designed for a small tube, asone having a screen two inches in diameter for displaying a single character at a time. With particular reference to FIGURE 4, the cathode-grid structure includes a plurality of cathode elements 35 each of which has an emissive surface 35a. The cathodes are mounted with their emissive surfaces in a single plane within a grid cup structure 36 having a planar closed end surface with a wire mesh grid 37 carried thereon. The grid cup 36 has a plurality of openings 36a in the closed end thereof, one associated with each of the cathodes 35. The grid mesh 37 is mounted on the inner surface of the grid cup, and the mesh size and spacings conform with the limits discussed above so that the grid exerts a control over the emission of electrons from each of the cathodes and forms the electrons into a plurality of discrete beams. Interposed between the emissive surfaces 35a of the cathodes and the closed end of the grid cup 36 is a masking member 38 which has a plurality of openings 38a therein, each associated with one of the cathodes, and each shaped to form a desired character, as illustrated in FIGURE 6.

The mask element 38 is operated at grid potential and serves to mask or block off some of the electron beams which would otherwise flow from the emissive surface of the cathode. Thus, only those beams which pass through the opening 381; in the mask reach the luminescent face or screen 39 of the tube. The size of the opening 38a is preferably such that the mask bundle is made up of from 10 to 50 individual beams. The electrons are accelerated, as by grid 40, and are then deflected to the axis of the tube by deflecting elements 41, here shown as electrostatic deflection plates, and which, it will be understood include provision for both vertical and horizontal deflection.

The resulting image on the screen 39 has the configuration of the character of the mask opening even though it is accelerated and deflected after masking. This action occurs because the bundle of discrete beams of electrons keeps the mask opening shape, and should be contrasted with the action of a single beam of electrons which tends to assume a circular cross section at all times. While a single beam may be masked, it will not retain its masked cross section, unless handled with great care, but Will return to a circular cross section after passing the mask. In the structure of FIGURE 4, the electrons are segregated into discrete beams as they come from the emissive surfaces of the cathodes, and they remain in that condition as they pass through the tube even though some 'of the individual beams are masked.

As illustrated schematically in FIGURE 4, the particular character desired at any time may be selected, as by switch means 42, which completes the circuit of a selected one of the cathodes 35. Obviously electronic switching may be substituted for the selector switch means 42 shown in FIGURE 4.

FIGURE 5 illustrates a modification of FIGURE 4 in which the grid cup 46 serves as the masking element. That is, the openings 46a in the closed end of the grid cup are shaped with the various desired configurations, as in araaees FIGURE 6. Again, a plurality of cathodes 45 are provided with emissive surfaces 45a which are aligned with the character openings 46a. The mesh screen 47, here mounted outside the grid cup 46, is so related to the emissive surfaces 45a of the cathode that the electrons emitted therefrom are formed into discrete beams which are partially masked by the openings 46a and thus formed into the desired cross-sectional configuration. The mesh screen 47 may be welded or brazed to grid cup 46, or may be pressed or swaged into the surface of the metal itself. In FIGURE 5, the closed end of the grid cup is curved and the emissive surfaces 35a of the cathode are so placed that the bundles of beams, which are accelerated by a similarly curved element 50, are directed at the desired position on the tube face 49. This eliminates the deflection system 41 which was provided in the. struc ture of FIGURE 4 to put the bundle of beams on the axis of the tube. Suitable switching means 53 may be provided for selecting the desired cathode, and thus the desired character to be displayed.

FIGURES 8 and 9 incorporate cathode-grid structures similar to those of FIGURES 4 and 5, and the same reference numerals are. used to indicate like parts. The tubes of FIGURES 8 and 9 are however designed to display the character information at any desired point of the tube screen. For this reason, additional deflection elements must be provided. In FIGURE 8, where the cathode-grid and accelerating elements are planar, a double deflection system 55 is required to deflect the shaped or masked bundles of beams onto the axis of the tube. A third deflection system 56 then deflects the image to the desired point on the screen. In FIGURE 9, where the cathodes, grid and accelerating element are curved so that the masked beams are directed toward a point on the tube axis, it is suflicient to provide two deflection systems. The deflection system 57 is located at the point in which the masked beams cross the tube axis and deflects these beams so that they travel along the axis to the second deflection system 58 which directs the beam to the desired point on the screen. The cathode switching means 42 and 53 may be tied in with the various deflection circuits to enable presentation of various types of information in various sequences and positions on the tube face.

The tubes of FIGURES 4, 5, 8 and 9 may be used in various ways. For example, the information may be visually observed on the tube screen. The tube may also serve as a storage or memory device in which the information is retained on the tube face and may be picked off at a later time by suitable scanning means.

I claim:

1. In a cathode-ray display tube, apparatus of the character described, comprising: a source of electrons including a cathode having an electron emissive surface; a grid having alternate solid portions and openings, said grid being located adjacent said cathode surface, the ratio of the width of the solid portions of the grid to the spacing therebetween being at least 0.05 and less than 0.5 and the ratio of the spacing between the solid portions of the grid to the spacing of the grid from the emissive cathode surface being at least 2.1 and less than 10, whereby a voltage applied between the grid and cathode establishes a varying voltage gradient across the emissive surface of the cathode to control the emission of electrons therefrom and to form said electrons into a plurality of discrete beams which comprise a bundle of electron beams; and means for masking a portion of said bundle of electron beams to give the bundle a desired cross-sectional configuration.

2. In a cathode-ray display tube, apparatus of the character described, comprising: a source of electrons including a cathode having an electron emissive surface; a grid having alternate solid portions and openings in a rectangular configuration, said grid being located adjacent said cathode surface, the ratio of the width of the solid portions of the grid to the spacing therebetween being at least 0.05 and less than 0.5 and the ratio of the spacing between the solid portions of the grid to the spacing of the grid from the emissive cathode surface being at least 2.1 and less than 10, whereby a voltage applied between the grid and cathode establishes a varying voltage gradient across the emissive surface of the cathode to control the emission of electrons therefrom and to form said electrons into a plurality of discrete beams which comprise a bundle of electron beams; and a plate having an opening therein positioned to intercept said bundle of beams, the opening in said plate defining a character and masking a portion of said plurality of electron beams to give said bundle a desired cross-sectional configuration.

3. In a cathode-ray display tube, apparatus of the character described, comprising: a source of electrons including a cathode having an electron emissive surface; a grid having alternate solid portions and openings, said grid being located adjacent said cathode surface, the ratio of the Width of the solid portions of the grid to the spacing therebetween being at least 0.05 and less than 0.5 and the ratio of the spacing between the solid portions of the grid to the spacing of the grid from the emissive cathode surface being at least 2.1 and less than 10, whereby a voltage applied between the grid and cathode establishes a varying voltage gradient across the emissive surface of the cathode to control the emission of electrons therefrom and to form said electrons into a plurality of discrete beams which comprise a bundle of electron beams; a mask having a plurality of openings therein, each defining a character; and means for directing a bundle of beams from said source through one of the openings of said mask to give said directed bundle of beams a desired cross-sectional configuration.

4. In a cathode-ray display tube, apparatus of the character described, comprising: cathode means having a plurality of independent emissive surface portions; control grid means associated with each of said surface portions and having alternate solid portions and openings located adjacent said cathode surface portions, the ratio of the width of the solid portions of the grid to the spacing therebetween being at least 0.05 and less than 0.5, and the ratio of the spacing between the solid portions to the spacing of the grid from said emissive surfaces being at least 2.1 and less than 10, whereby a voltage applied between said grid and said cathode surfaces establishes a varying voltage gradient across each of said emissive surface portions to control the emission of electrons therefrom and to form said electrons into a plurality of discrete beams, the beams from each cathode surface portions comprising a bundle of electron beams; mask means having a plurality of openings therein each defining a character and each mask opening being generally aligned with the path of a bundle of beams from one of said cathode surface portions; and means for selectively passing a bundle of beams from one of said emissive portions through an opening in said mask means.

5. The display tube of claim 4 wherein said last-named means includes means for controlling conduction of a circuit connected with each of said portions of the cathode means.

6. In a cathode-ray display tube, apparatus of the character described, comprising: a source of electrons including a cathode having an electron emissive surface; a grid structure having alternate solid portions and openings in a rectangular configuration, said grid being located adjacent said cathode surface, the ratio of the width of the solid portions of the grid to the spacing therebetween being at least 0.05 and less than 0.5 and the ratio of the spacing between the solid portions of the grid to the spacing of the grid from the emissive cathode surface being at least 2.1 and less than 10, whereby a voltage applied between the grid and cathode establishes a varying voltage gradient across the emissive surface of the cathode to control the emission of electrons therefrom and to form said electrons into a plurality of discrete beams which comprise a bundle of beams; a mask having an opening therein defining a character, said mask being associated with said cathode and grid to mask a portion of the beams; and means connecting said mask at the same potential as said grid.

7. The cathode-ray tube of the character described in claim 6 wherein said mask is interposed between said emissive surface and said grid structure.

8. The cathode-ray tube apparatus of the character described in claim 6 wherein said grid structure is interposed between said emissive surface and said mask.

Maloif Jan. 4, 1938 Schlesinger Feb. 25, 1941 8 Thompson Aug. 26, 1941 Broadway May 12, 1942 Schlesinger Dec. 29, 1942 Taylor Mar. 1, 1949 Steinhardt Aug. 7, 1956 McNaney Sept. 4, 1956 Glyptis May 13, 1958 Bryan July 22, 1958 McNaney Nov. 25, 1958 Glenn Jan. 6, 1959 Nicoll Mar. 10, 1959 Frenkel Mar. 31, 1959 FOREIGN PATENTS Great Britain May 31, 1940

Claims (1)

1. IN A CATHODE-RAY DISPLAY TUBE, APPARATUS OF THE CHARACTER DESCRIBED, COMPRISING: A SOURCE OF ELECTRONS INCLUDING A CATHODE HAVING AN ELECTRON EMISSIVE SURFACE; A GRID HAVING ALTERNATE SOLID PORTIONS AND OPENINGS, SAID GRID BEING LOCATED ADJACENT SAID CATHODE SURFACE, THE RATIO OF THE WIDTH OF THE SOLID PORTIONS OF THE GRID TO THE SPACING THEREBETWEEN BEING AT LEAST 0.05 AND LESS THAN 0.5 AND THE RATIO OF THE SPACING BETWEEN THE SOLID PORTIONS OF THE GRID TO THE SPACING OF THE GRID FROM THE EMISSIVE CATHODE SURFACE BEING AT LEAST 2.1 AND LESS THAN 10, WHEREBY A VOLTAGE APPLIED BETWEEN THE GRID AND CATHODE ESTABLISHES A VARYING VOLTAGE GRADIENT ACROSS THE EMISSIVE SURFACE OF THE CATHODE TO CONTROL THE EMISSION OF ELECTRONS THEREFROM AND TO FORM SAID ELECTRONS INTO A PLURALITY OF DISCRETE BEAMS WHICH COMPRISE A BUNDLE OF ELECTRON BEAMS; AND MEANS FOR MASKING A PORTION OF SAID BUNDLE OF ELECTRON BEAMS TO GIVE THE BUNDLE A DESIRED CROSS-SECTIONAL CONFIGURATION.

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