US3564320A - Electrode mounting structure for cathode ray tubes - Google Patents

Abstract

A character display system has a plurality of small cylindrical side-by-side cathode-ray tubes about .8 inch in diameter and less than 4 inches long, aligned to form a line of individual characters. The tubes have structure for precisely aligning the characters uniformly including an electron gun fashioned to center the electron beam by means of electrostatic deflection electrode pairs held in two glass beads oriented with a seven pin miniature glass stem to produce two normal deflection axes. Similar electrode structure is employed for a plurality of electrodes in the gun formed of a rectangular shaped blank held at opposite ends in the two beads, and a set of snubber springs is affixed to one such electrode oriented toward the stem to and in centering the gun within the tube cylindrical walls.

Description

United StatesQPatent Inventor Horst H. Blur'nenberg Owensboro, Ky. Appl. No. 861,600 Filed Sept. 29, 1969 Patented Feb. 16, 1971 f Assignee Kentucky Electronics, Inc.

Owensboro, Ky. Continuation-impart of application Ser. No. 843,296, July 22, 1969.

ELECTRODE MOUNTING STRUCTURE FOR CATHODE RAY TUBES 3 Claims, 5 Drawing Figs.

US. Cl 313/82; 313/5 3131251 Int. Cl. H0lj 29/02, H0 1 j 29/46 Field ol'Sear-ch 3 l 3/109.5, 82

References Cited UNITED STATES PATENTS 2,266,773 12/1941 Law 313/82X 2,496,825 2/ 1950 Szegho 313/82 2,516,704 7/1950 Kohl 313/7 2,781,474 2/1957 Coleman 315/21 2,859,378 11/1958 Gundert et al... 315/13 2,975,315 3/1961 Szegho 313/82 3,215,880 11/1965 Krackhardt 313/82 FOREIGN PATENTS 957,087 5/1964 Great Britain 313/82 Primary ExaminerRobert Segal Anomey Laurence R. Brown ABSTRACT: A character display system has a plurality of small cylindrical side-by-side cathode-ray tubes about .8 inch in diameter and less than 4 inches long, aligned to form a line of individual characters. The tubes have structure for precisely aligning the characters uniformly including an electron gun fashioned to center the electron beam by means of electrostatic deflection electrode pairs held in two glass beads oriented with a seven pin miniature glass stem to produce two normal deflection axes. Similar electrode structure is employed for a plurality of electrodes in the gun formed of a rectangular shaped blank held at opposite ends in the two beads, and a set of snubber springs is affixed to one such electrode oriented toward the stem to and in centering the gun within the tube cylindrical walls.

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" RACTER GENERAT I 1 AND SELECTION CIRCUITS l5 FIG.|

INVENTOR ATTORNEY HORST H; BLUMENBERG PA ENI n rm 1 s an f, sum 2 ur z' if I YIII/IIIIIII. 'IIIIIIIIIIA INVENTOR HORST H. BLUMENBERG ATTORNEY ELECTRODE MOUNTING STRUCTURE FOR CATHODE RAY TUBES This application is a continuation in part of my copending U.S. application for indicia Forming Cathode Ray Tubes, Ser. I

No. 843,296, filed July 22, 1969.

This invention relates to character display devices and more particularly it relates to cathode-ray tube displays for generating a line of separate characters in individual side-by-side tubes.

Display devices responsive to electronic signals to generate visual characters such as numbers or alphabets are known, which operate in different modes. Many such devices are deficient in several important aspects.

If mechanical devices are used, they do not follow electrical signals adequately or quickly enough and they are difficult to synchronize.

Cathode glow and phosphor display devices are low in brightness. Most of these provide parallax problems and do not show parts of the characters formed. Also they are not adaptable to variations of characters and such symbols as the dollar sign or letters in Hebrew or Arabic which require specialtooling. Also a limited number of different characters can be displayed, in general. v

Cathode-ray tube devices in the prior art have not been competitive in price with low-cost display tubes. Some have required custom tubes with built in masks or special features for generating character shapes. Generally, an entire line of would require custom built envelope sizes and specialized deflection systems. Individual tubes used for generating each character would be too expensive in both tube design and system requirements when using prior art techniques. For example oscillographic centering structure such as horizontal and vertical centering potentiometers used in orienting placement and skew of the different characters placed ina line by means of standard CRT techniques would be prohibitive in price when applied to a plurality of individual tubes.

Accordingly, it is an object of this invention to provide improved character display devices correcting the foregoing deficiencies.

A more specific object of the invention is to provide specially constructed cathode ray tube indicia generating devices which are economically and technically feasible within required geometry and electrical restrictions imposed in producing side-by-side characters of uniform size and skew in very small spaces with tubes less than 1 inch in diameter.

Therefore, in accordance with this invention, individual cathode-ray tubes placed side by side in line to fonn a line of characters are each made with cylindrical envelopes of less than 4 inches in length and .8 inch in diameter to display individual characters of any desired shape by scanning an electron beam electrostatically along two normal axes.

To provide acceptable alignment, each tube has an electron gun with electrodes precisely positioned and oriented to produce ajbeam centered on the phosphor screen raster area of approximately .625 inches maximum deflection provided for character formation. This alignment is accomplished in part by use of rectangular shaped electrode plates which are held in two spaced glass beads oriented carefully in the center of the cylindrical envelope relative to a seven pin miniature stem to define two normal deflection axes precisely within less than 3.

Those features of novelty afforded by this invention together with further objectives and advantages of the invention are illustrated by the preferred embodiment shown in the accompanying drawings, wherein:

FIG. 1 is a schematic block diagram of a character display system incorporating a plurality of side-by-side cylindrical cathode-ray tube character-generating devices in accordance with the provisions of this invention.

FIG. 2 is a perspective view of a cathode-ray tube character generator afforded by the invention.

FIG. 3 is a plan view of an electrode plate structure provided by the invention.

FIG. 4 is an elevation schematic view of the electrode assembly and connections to a miniature seven-pin stem, and

FIG. 5 is an elevation view of a cylindrical cathode-ray tube partly broken away to show the electrode and connecting strap relationships within the tube.

In FIG. 1 a set of separate cylindrical envelope CR display tubes 10, 10' etc. is aligned along horizontal deflection axis 12 with their phosphor faceplates substantially in the same plane. Each tube 10 has a vertical deflection axis 11 which intersects at the center of the display with the horizontal deflection axis 12.

When forming a line of separated characters, the alignment and skew is critical if misalignments visually detectable are to be avoided. For this reason a character forming tube for presenting a single character-is critical in construction and must afford a combination of features which will provide precise centering and deflection alignment in each individual tube without the necessity for external adjustment or manipulation of electronic circuits. Conventional tube construction techniques in a tube of the very small size required with a screen diameter of less than 1 inch which would permit the beam to be off center as illustrated in tubes 10 and 10 by the dots, or which would allow deflection skew as illustrated in tubes 10" and 10" would be unacceptable in forming a line of characters. The eye is very sensitive in sensing character alignment, and even a small degree of skew or misalignment is readily noticed as evidenced by viewing typewritten text when a type bar is slightly displaced, for example.

Character displays of any design can be generated for electrostatically deflecting the cathode-ray beam to form the numerical characters 2 illustrated, or other desired pattern. Deflection techniques of this type are well known and are represented by the block circuit diagram 15. The state of the art may be exemplified for example by reference to U.S. Pat. No. 3,432,845 issued Mar. 1 l, 1969, where numerical characters are produced. It is to be noted that a CRT display of the type provided by this invention is not restricted to any one set of characters or any limitationson' variations or total number of characters possible. Also, by use of a P-l phosphor, the brightness significantly exceeds that generally available with cathode glow, phosphorescent or other displays which generate their own light source.

Each tube is separately driven; at grid lead 17 and the horizontal and vertical deflection axes at leads 18, 19 by character generator subsections l6, 16' etc. to produce the desired line of text. In order to display a line of characters on individual tubes it is significant that the tube shape is cylindrical or equivalent nonflared shape with substantially symmetrical sidewalls permitting the tubes to be placed closely together side by side along axis 12 and does not constitute a flared-out screen section found in conventional cathode-ray tube oscillograph tubes.

Thus a tube 10 is preferably constructed as shown in FIG. 2, with a cylindrical envelope having an axis 32 along which an electron beam is nominally directed in absence of electrostatic deflection voltages. Electrostatic deflection plates permit the tubes to be placed side by side without interference between tubes. In this tube, the electron gun 30 is physically positioned in a precise manner to assure that the electron beam is directed along centerline 32. This requires care in orienting each gun and deflection electrode exactly in place to be held firmly by a pair of glass beads 31. The beads are oriented in the region of exhaust stem 39 and the miniature seven pin button to precisely align the deflection axes with respect to the pin socket positions. Thisis done by straps or metallic posts welded carefully in place between the electrodes and the pins inside the tube envelope to serve as leads and mounts to orient the deflection plates and stem in exact alignment. To assure the centering of the beam within the cylindrical tube envelope, a set of special snubber springs is provided as hereinafter described to center the electron gun at a position remote from the stem.

in order to facilitate alignment and jigging for the precise electrode spacing and to seal the electrodes in the glass bead without distortion, electron lens electrodes 41, 53, 54, 55 are made rectangular in shape as shown in FIG. 3, to thus be embedded in the beads at opposed ends. To permit electron gun flexibility with this preferred structure, the centered beam aperture is selectively punched to the desired size for each electrode but, otherwise, the various electrodes are similar, to provide both low cost and better electron gun electrode alignment as well as performance.

This critical snubber mount position is referenced in place in FIG. 4, where the snubber electrode or shield is held at ground potential by connections to lead 65. The snubber plate 41 is physically mounted between beads 50, 51 in a position intermediate the two pairs of deflecting electrodes. The accelerating potential is applied between terminals 65 and 68.

The internal connections to the seven pins are illustrated, where grounded pin 65 leads to electrodes 41, 54, 55 and one electrode 63, etc., of each pair of deflection electrodes. Other connections are made to the heater pin 66 and to the grid pin 67. Each deflection axis is available at a separate pin 69 and 71 connecting with respective deflection plates 64 and 62. A focus electrode such as cylinder 61 or an equivalent apertured plate structure is connected at pin 70 to make available all the necessary electrode controls in a miniature seven-pin stem.

The gun structure has to be inexpensive to produce a competitive display tube and yet very critical tolerances must be met. These tubes are constructed with a centering requirement for an undeflected beam to lie within one-half millimeter of the center of the tube in the scanning region on the phosphor coated screen. Also the horizontal and vertical deflection axes are oriented to within 3 of a reference axis defined by the orientation of the pins in the seven-pin miniature stem. These requirements must be considered in view of the sensitivity of the beam to electrode positions and defects, and the normal tolerances of jigs with thermal changes of dimensions and stresses, etc. The very small dimensions of the tube with a nominal cylinder diameter of .788 inches, tube length of 3.5 inches overall and useful screen deflection of .625 inches, make the requirements even more critical.

These requirements are met, however, by the array shown in FIG. 4 where the electrodes are all aligned precisely between glass beads 50 and 51, held rigidly in place by the rectangular structure of the various electron gun electrodes 53, 54, 55 and 41 spaced along the gun structure. This physically orients the electrodes precisely enough to direct the beam along a well-defined axis which is centered within the cylindrical tube envelope by the snubber springs to direct an undeflected spot precisely along the axis of the tube.

Also the deflection plates are oriented along normal axes by the beads 50 and 51 to provide closely aligned deflection axes. Simple electrode structures, such as the deflection plate 64 which is a single flat plate bent along a straight line, provide for a minimum of distortion of the beam by defects, corona or the like.

The rectangular lens structure with the oppositely extending tabs mounted in the pair of parallel glass beads permits also an improved and simplified cathode mounting. Among their advantages is the simplicity of jigs for holding the electrodes exactly in position while affixing a glass bead.

A cylindrical metallic cathode cup 57-59 is affixed by a tab to the rectangular plate 52 without an intermediary ceramic disc or other insulator. The cathode cup 59 is preferably surrounded by a cylindrical shield 60 which is affixed to the plate by a suitable tab portion. The shield 60 serves simultaneously to electrically shield the cathode emission surface, provide proper heat conduction and dissipation characteristics and permit precise axial spacing of the cathode relative to control grid 67 while maintaining exact alignment of the cathode with the axis of the tube.

The overall tube perspective is shown from the view of FIG. 5, from the miniature seven-pin stem 29 to the phosphorcoated face 80, wherein connection 65 corresponds to the connection schematically shown in FIG. 4. An accelerating electrode inside the envelope comprising aquadag coating 81 is contacted by a snubber spring assembly 42 attached to rectangular electrode 41 formed as shown in FIG. 3.

In this tube the requirements for strict electrode alignment and very small space is accomplished by use of the rectangular electrode structure. Very simple alignment jigs may be used and these electrodes functionally aid the electrostatic lens field formation, the shortness of the overall tube, the ease of electrode connection and the ability to make the electrodes and assemble the tube at reasonable cost. Note the notched edges of the rectangular electrode structure. The notches when symmetrically spaced prevent misalignment of the electron lens that could occur with irregular shapes and provides means for precise alignment of the parts. For this purpose, the

center aperture and the notches are cut with a single die to always maintain identical spaced relationships. Also the notches can functionally aid in connecting the electrode strap 65 for example as hereinafter described.

When the edges of electrodes 41, 63, 55 and 54 are disposed in the same plane parallel to the beam axis, the connecting strap 65 may be simply welded to the edges. lf several electrodes are encompassed by the strap, it may bypass certain electrodes such as the cylindrical focus electrode 61 having a diameter small enough to prevent extending into the plane, or by notches in the edge of the rectangular plates.

In the embodiment shown, spaced deflecting plates of the pair 62 and 63 have edges resting in the plane, but the path of strap 65 only passes over electrode 63. Rectangular plate 41 is located between two pairs of deflection plates so that the terminal end of strap 65 may be welded to a part of flared deflection electrode 64 that does not lie in the plane.

It is therefore clear that the novel arrangement of electrodes in this tube structure afford improved operation and simplified construction particularly in a miniature cathode-ray tube that must be precisely matched with others for indicia generating applications.

lclaim:

1. A single gun cathode-ray tube assembly providing an axially centered cathode ray beam path comprising in combination, an envelope having a phosphorous screen, an electron gun arrangement with a plurality of spaced electrodes affixed in an ordered array extending along said axial path of the cathode-ray beam by means of insertion of the electrodes into two spaced molten beads into which the electrodes are extended and 'means therewith to hold the beads firmly in a central position within said envelope thereby to align the beam axis coaxially within the envelope and to hold and direct the beam along a precisely directed axial path to strike a predetermined position on said screen, said spaced electrodes of said plurality being flat, rectangular plates of the same size, each having a single centered aperture therein and longitudinal edges embedded in said spaced beads, and further having unembedded edges substantially lying in a common plane parallel to the beam axis defined by the single centered apertures of said plates, said electron gun arrangement further including interspersed with said flat electrodes cylindrical electrodes of a sufficiently small diameter as not to extend into the planes defined by the edges of said flat rectangular electrodes, a plurality of said rectangular electrodes further having sub stantially coplanar edges in a plane substantially parallel to said beam axis, and a connecting strap extending in said plane and being attached to said coplanar edges.

2. A cathode ray tube assembly as defined in claim 1, including a set of two deflection plates having edges in said plane, and connections from said strap to the edge of one of such deflection plates.

3. A cathode-ray tube assembly as defined in claim 1 wherein opposite edges of said flat plates not embedded in said beads are provided with alignment notches extending inwardly from said common plane, which notches are precisely spaced relative to the single centered apertures therein to provide alignment guides for precisely aligning the centered apertures along said beam axis coaxially within said envelope.

Claims (3)

1. A single gun cathode-ray tube assembly providing an axially centered cathode ray beam path comprising in combination, an envelope having a phosphorous screen, an electron gun arrangement with a plurality of spaced electrodes affixed in an ordered array extending along said axial path of the cathode-ray beam by means of insertion of the electrodes into two spaced molten beads into which the electrodes are extended and means therewith to hold the beads firmly in a central position within said envelope thereby to align the beam axis coaxially within the envelope and to hold and direct the beam along a precisely directed axial path to strike a predetermined position on said screen, said spaced electrodes of said plurality being flat, rectangular plates of the same size, each having a single centered aperture therein and longitudinal edges embedded in said spaced beads, and further having unembedded edges substantially lying in a common plane parallel to the beam axis defined by the single centered apertures of said plates, said electron gun arrangement further including interspersed with said flat electrodes cylindrical electrodes of a sufficiently small diameter as not to extend into the planes defined by the edges of said flat rectangular electrodes, a plurality of said rectangular electrodes further having substantially coplanar edges in a plane substantially parallel to said beam axis, and a connecting strap extending in said plane and being attached to said coplanar edges.

2. A cathode ray tube assembly as defined in claim 1, including a set of two deflection plates having edges in said plane, and connections from said strap to the edge of one of such deflection plates.

3. A cathode-ray tube assembly as defined in claim 1 wherein opposite edges of said flat plates not embedded in said beads are provided with alignment notches extending inwardly from said common plane, which notches are precisely spaced relative to the single centered apertures therein to provide alignment guides for precisely aligning the centered apertures along said beam axis coaxially within said envelope.

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