US3188506A - Cathode ray tube with signal plate connected to contact ring having envelope diameter - Google Patents

Description

June 8, 1965 M. ROME CATHODE RAY TUBE WITH SIGNAL PLATE CONNECTED TO CONTACT RING HAVING ENVELOPE DIAMETER Filed NOV. 25, 1959 AGENT United States Patent() 3,158,506 CATHODE RAY TUBE WITH SIGNAL PLATE CUN- NECTED Tt) CQNTACT litlNG HAVING ENVE- `I iOlWE DIAMETER Martin Rome, Stamford, Coun., assigner to The Machlett Laboratories, incorporated, Springdale, Conn., a corporation .of Connecticut Filed Nov., `23, 1959, Ser. No. 854,656 3 .Claims (Cl. 313-65) This invention relates to cathode ray tubes and more particularly -to cathode ray tubes of the vidicon type `having novel `electrode structures within the envelope thereof.

ln various types of cathode ray tubes suitable for use as pickup `tubes for television purposes, some electrodes extend through a substantial length of the envelope but are supported at only one end. For example, an electron gun comprised of a cathode and a plurality of longitu dinally-spaced auxiliary electrodes joined by dielectric supporting means is supported at one `end of the envelope i `on relatively thin terminal leads, and extends Well into the envelope `from the leads. The inner of said plurality of electrodes generally carries a long tubular shield which, in some tubes, terminates near the opposite end of the envelope in a transversely .disposed iine mesh screen. This end of the gun structure is generally snpported upon the glass wall by flexible spacers or by an encircling ring.

However, under severe conditions of vibration, such as occur when a television camera is being moved or, more particularly, ,in industrial television installations where the surroundings are sometimes conducive to excessive vibrations, or in installations in space missiles and the like Where the engines tend to promote vibrations of the electrodes, relative `motions of the gun, mesh, and envelope cause microphonics which are apparent in the displayed image as' striations in the line str`ucture, resulting in pic- `ture distortion. Such vibrations, furthermore sometimes `dislodge small particles of metal from welded joints, which particles can damage the photosensitive layer on the target.

ln `conventional prior art tubes of this type another disadvantage resides in the diiiiculty in outgassing electrodes which are located near the photosensitive target. `Outgassing by conventional RP. heating may damage the photosensitive material.

The present invention overcomes such disadvantages of prior art tubes by the provision of novel means ofiixedly securing electrode structures within the envelopes so that vibrations will not aiiect the eflicient operation of the `electrodes or the quality of the resultant images. This is accomplished by conventionally supporting the terminal `end `of the electron gun structure in a suitable manner at one end of the tube, by providing the guns innermost electrode with a predetermined peripheral coniiguration which is supported by a circumferential area of the envelope in such a manner that conduction takes place between the portion and a conductive coating on the inner wall `of the envelope. The coating is physically connected `to a mesh-type grid electrode which is rigidly secured about its periphery to the inner Wall of the envelope at the opposite end of the tube adjacent -a xed photosensitive target carried directly upon the faceplate. The metal coating is deposited in high vacuum on the inner wall of envelope and is substantially gas-free by virtue of its ex- Atreme thinness `in comparison with conventional structures. Additionally, in the presently described tube structure,

:barriers are provided at the inner end of the gun and at the grid electrode which prevent small particles dislodged from welds in the gun from reaching the target area.

Accordingly, it is a primary object of the present invention to provide an improved cathode ray `tube which is substantially resistant to and unaiiected by vibration.

Another object is to provide novel electrode structures for cathode ray tubes and novel means of supporting the electrodes within the envelopes of the tubes.V

Another object is to provide a cathode ray tube having especially rug-ged `and durable characteristics..

Another object is to provide a cathode ray tube wherein the electron gun structure is rigidly supported and the target and mesh structures are secured rigidly to the inner walls of the tube envelope.

`Still another object is to provide a cathode ray -tube having an electron gun at one end and a grid at the other end, and having novel `means for maintaining the grid at the same potential as the nearest electrode Ain the electron from reaching the area of the target.

A still further object is the provision oi a novel tube wherein the target structure will not be damaged by outgassing processes.

Other objects and advantages will become apparent from the vfollowing description taken in connection with the accompanying drawing wherein:

FIG. l is an axial sectional view of `a pickup tube constructed in accordance with this invention;

FIG. 2 is an enlarged axial sectional view ot the target and mesh structures; and

FlG. `3 is an enlarged axial sectional view of a portion of the electron gun structure `illustrating in exaggeration the fixed mounting for the electron gun.

The tube structure embodying the invention comprises a rrelatively long, slender, cylindrical, vacuum-tight envelope or bulb 10 of glass having a target structure 11 within one end and `having within the other end an electron gun structure ft2 which is adapted to form `an electron beam for the purpose of scanning the target `lil in the normal operation of a tube of this type.

The electrodes of the electron gun l2 include` a cathode 13, a control electrode 14, and a plurality of auxiliary electrodes such as first accelerating electrode 15 and focusing electrode 16, which are suitably connected'to respective lead-in pins or terminals i7 in the well-known manner.

A filament or heater 18 Withinthe cathode 13 is adaptedto heat thejcathode to the temperature necessary to cause copious liberation of electrons from the cathode. The electrons are drawn through the electrodes and are simultaneously formed into a beam which is ,adapted to scan the target 1l. In passing through the tube iromthe focusing electrode 16 to the target lll, the electron beam is under the iniiuence of an extended portion 20 ofthe electrode la which is in the form of a vaporized metallic coaton the inner Wall of the bulb 10. The `electrodes 14, l5 and 16 are all apertured, cylinrical, cup-like electrodes which are maintained in aligned and properly spaced retlation by ceramic insulating posts 2l to which each electrode is secured independently of the other electrodes. Electrode lr6 is, more specically, a hollow cylindrical member 22 (-FIG. `3) having both closed ends provided with apertures 23 through which the electron beam passes. Member 22 is provided with an outstanding peripheral flange 24,` preferably adjacent its -end nearest the target ll, which flange is mounted upon the inner wall of envelope lil between two very shallow' ledges 25 of glass. The ledges 25 are preferably yformed by softening the glass wall of the envelope in the circumferential area encircling the iiange 24 to the extent neces- Patented June 8, 1965 the flange 24.

sary to allow the inner surface to collapse slightly around an-d interiit with the edge of the flange. When the glass is subsequently hardened and annealed, the inner surface will assume the shape shown exaggeratedly in FIG. 3, with the ledges snugly interfitting with the edge of the flange 24, thus securely retaining the electrode f6 and, consequently, the entire gun assembly f2 in place.

I have found that the inner surface of the envelope il@ can be softened and drooped slightly over the flange 2d to form the-ledges 25 without damaging the vaporized metallic coating Ztl. Thus, in the iinal structure the thin metal coating Z remains continuously unbroken and overlies the ledges and the peripheral edge portion of In this way extremely efficient electrical contact is maintained between the member 22 and the coating 20 without requiring separate lingers or other devices for this purpose.

The opposite end of the tube is provided with a transparent faceplate Z6 which is initially formed as a separate glass disc provided on one side with a transparent coating or layer 27 of Vconductive material such as tin oxide. The coated surface 2'7 may be sealed to the open end of the bulb 10 as shown in FIG. 2 and an annular metal terminal ring 23 sealed in encasing relation to the faceplatebulb seal and the adjacent portions of the peripheral edges of both the faceplate and end of the bulb lil. Ring 23, being in direct engagement with coating 27, functions as a terminal for the target 1f.

On the exposed surface of the transparent conductive coating 2'7, there is provided a layer 29 of photosensitive material such as any of the photoconductive materials which are responsive to visible light or to invisible radiations. For example, selenium, antimony sulfide, or other materials sensitive to visible light may be used, or cadmium sulphide, lead sulphide, or any of the other materials which are known to be responsive to X-rays, gamma rays or other invisible radiations. The layer 2,9 of photosensitive material, however, preferably does not extend to the seal between the faceplate 26 and bulb l0.

A grid electrode 3d, in the form of a relatively ne mesh which is permeable to the electron beam, is positioned adjacent the target 11 and, during operation of the tube, functions together with external focus coils (not shown) to insure that the electron beam in its iinal approach to the surface of target lll is normal thereto.

The grid 30 is rigidly mounted within the bulb or envelope 10 by means of a rigid metal annulus 3l which is rigidly sealed throughout its periphery by a suitable glassmetalseal to a shallow annular ledge 32 (shown in great exaggeration in FG. 2) formed on the inner surface of Ythe bulb itl. If desired, the'grid mesh may be made as a sandwich wherein they edge of the mesh is retained between two such annuli, at least one of which is sealed directly tothe wall of the envelope A.by the ledge 32. It is .to be noted that ledge 32 is extremely shallow and is formed by heating the'bulb in the area encircling the grid to the extent where the glass collapses slightly into close embracement of annulus Sil.

It is particularly important in this structure to extend the vaporized metallic coating 20 over the surfaces of the Vledge 32 and annulus 3l which face the gun 12. In this way-the grid tl, coating 2l), and focusing electrode member 22 are all maintained at the same potential.

structures. Such ruggedness is considerably enhanced by the particular electrode mounting structures described whereby the electrodes'are not suspended within the enr4velope only upon relatively fine wirelike supports con- Y ducive to vibrations but are, instead, securely and rigidly mounted directly upon the inner wall of the envelope. Such a'structure also permits the focusing electrode to be continuous throughout the length of the tube from the ,reason electron gun to the grid adjacent the target whereby the focusing electrode and grid may be maintained at the same potential, thus eliminating the need for providing separate leads and terminals for various portions of the electrode structures such as are required in known prior art tubes. The number of welded joints is considerably reduced in the presently described structure, and the particular mountings of the focusing and grid electrodes aid in preventing particles dislodged rfrom welds in the gun from reaching the target. Y

In the presently described tube, electrical leads for connecting all the electrodes to their respective sources of potential all extend out of the envelope through one end of the tube except the target lead which is provided as a ring.

t will also be apparent that all of the objects and advantages of this invention are accomplished and achieved by the tube structure described above] However, it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention as expressed in the accompanying claims.

l claim:

l. A cathode ray tube comprising an evacuated dielectric envelope embodying a tubular bulb having one end sealed and having the otherend closed by a transparent faceplate sealed to the end of the bulb, an electron gun structure at the sealed end of the envelope, and a target on the inner side of the faceplate and arranged to be scanned by an electron beam from the electron gun, the electron gun including a cathode and at least one electrode spaced longitudinally of thev bul-b inwardly from the cathode, the target comprising a thin transparent layer of electrically conductive material covering substantially the entire inner surface of the faceplace and extending through the seal between the faceplate and end of the bulb, a layer of photosensitive material on the conductive layer entirely within the interior of the bulb, and a terminal for the target comprising a metal ring closely enclosing the edge of the faceplate and in abutting relation to the periphery of the conductive layer, the ring being sealed directly to the end of the bulb and having an outer diameter substantially equal to the outer diameter of the adjacent portion of the bulb.

2. A cathode ray tube comprising an evacuated dielectric eneveloperembodying a tubular bulb having one end sealed and having the other end closed by a transparent faceplate sealed to the end of the bulb, anrelectron gun structure at the sealed end of the envelope, and a target on the inner side of the faceplate and arranged to lbe scanned by an electron beam from the electron gun,

from the grid to the electrode, the target comprising a thin transparent layer of metal covering substantially the entire inner surface of the faceplate and extending through the seal between the faceplate and end of the bulb, a

vlayer of photosensitive material on the metal layer entirely within the interior of the bulb, and a terminal for the target comprising a metal ring closely enclosing the edge of the faceplate and in abutting relation to the periphery of the metal layer, the ring being sealed directly to the end of the bulb and having an outer diameter substantially equal to the outer diameter of the adjacent portion of the bulb. n

3. A cathode ray tube comprising an evacuated dielectric envelope embodying a tubular bulb having one end sealed and having the other end closed by a transparent faceplate sealed to the end or" the bulb, an electron gun structure at the sealed end of the envelope, and a target on the inner side of the faceplate and arranged to be scanned by an electron beam from the electron gun,

the electron gun including a cathode and at least one electrode spaced longitudinally of the bulb inwardly from the cathode, a grid in the bulb adjacent the target, the grid and electrode having annular portions extending toward the envelope and rigidly supported thereon, and a metal coating on the inner Wall of the bulb extending from the grid to the electrode and in direct engagement therewith whereby the coating and grid are maintained at the same potential as the electrode, the target comprising a thin transparent layer of metal covering substantially the entire inner surface of the faceplate and extending through the seal between the faceplate and end of the bulb, a layer of photosensitive material on the metal layer entirely within the interior of the bulb, and a terminal for the target comprising a metal ring closely enclosing the edge of the faceplate and in abutting relation to the periphery of the metal layer, the ring being sealed directly to the end of the bulb and having an outer diameter substantially equal to the outer diameter of the adjacent portion of the bulb.

References Cited by the Examiner UNITED STATES PATENTS Chilcot et al B13-244 X Goodrich.

Best S15- 3.5 X Geiger 315- Rotow et al.

Anderson e 29-25.13 Cassman 313- X Booth et al, 29--25.13 Salgo.

Cope.

Fotlant 313-65 X 15 GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, Examiners.

Claims (1)

1. A CATHODE RAY TUBE COMPRISING AN EVACUATED DIELECTRIC ENVELOPE EMBODYING A TUBULAR BULB HAVING ONE END SEALED AND HAVING THE OTHER END ENCLOSED BY A TRANSPARENT FACEPLATE SEALED TO THE END OF THE BULB, AN ELECTRON GUN STRUCTURE AT THE SEALED END OF THE ENVELOPE, AND A TARGET ON THE INNER SIDE OF THE FACEPLATE AND ARRANGED TO BE SCANNED BY AN ELECTRON BEAM FROM THE ELECTRON GUN, THE ELECTRON GUN INCLUDING A CATHODE AND AT LEAST ONE ELECTRODE SPACED LONGITUDINALLY OF THE BULB INWARDLY FROM THE CATHODE, THE TARGET COMPRISING A THIN TRANSPARENT LAYER OF ELECTRICALLY CONDUCTIVE MATERIAL COVERING SUBSTANTIALLY THE ENTIRE INNER SURFACE OF THE FACEPLATE AND EXTENDING THROUGH THE SEAL BETWEEN THE FACEPLATE AND END OF THE BULB, A LAYER OF PHOTOSENSITIVE MATERIAL ON THE CONDUCTIVE LAYER ENTIRELY WITHIN THE INTERIOR OF THE BULB, AND A TERMINAL FOR THE TARGET COMPRISING A METAL RING CLOSELY ENCLOSING THE EDGE OF THE FACEPLATE AND IN ABUTTING RELATION TO THE PERIPHERY OF THE CONDUCTIVE LAYER, THE RING BEING SEALED DIRECTLY TO THE END OF THE BULB AND HAVING AN OUTER DIAMETER SUBSTANTIALLY EQUAL TO THE OUTER DIAMETER OF THE ADJACENT PORTION OF THE BULB.

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