US3885191A

US3885191A - Cathode-grid assembly for a cathode ray tube

Info

Publication number: US3885191A
Application number: US448681A
Authority: US
Inventors: Donald R Kerstetter
Original assignee: GTE Sylvania Inc
Current assignee: GTE Sylvania Inc
Priority date: 1974-03-06
Filing date: 1974-03-06
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20

Abstract

A cathode-grid assembly for a cathode ray tube comprises a substantially cup shaped grid having a closed end containing a substantially centrally located aperture and a projecting contiguous side wall. The closed end and the side wall define a hollow interior. A cathode and a cathode support are positioned and fixed within the hollow interior of the grid. The cathode comprises a hollow metallic sleeve closed at one end by a cathode cap the outermost surface of which contains an electron emissive material. The cathode support comprises an electrically insulating member of a size to fit within the hollow interior of the grid and has upper and lower surfaces. A substantially centrally located cathode aperture interconnects the upper and lower surfaces of the support. First means extend from the lower surface of the support for mounting the support within the hollow interior of the grid and second means also extend from the lower surface of the support for mounting the cathode.

Description

United States Patent [191 Kerstetter CATHODE-GRID ASSEMBLY FOR A CATHODE RAY TUBE [75] Inventor: Donald R. Kerstetter, Emporium,

[73] Assignee: GTE Sylvania Incorporated,

Stamford, Conn.

[22] Filed: Mar. 6, 1974 [21] Appl. No.: 448,681

Primary Examiner-Robert Segal Attorney, Agent, or FirmNorman .1. OMalley; William H. McNeill; Cyril A. Krenzer 1 May 20, 1975 {57} ABSTRACT A cathode-grid assembly for a cathode ray tube comprises a substantially cup shaped grid having a closed end containing a substantially centrally located aperture and a projecting contiguous side wall. The closed end and the side wall define a hollow interior. A cathode and a cathode support are positioned and fixed within the hollow interior of the grid. The cathode comprises a hollow metallic sleeve closed at one end by a cathode cap the outermost surface of which contains an electron emissive material. The cathode support comprises an electrically insulating member of a size to fit within the hollow interior of the grid and has upper and lower surfaces. A substantially centrally located cathode aperture interconnects the upper and lower surfaces of the support. First means extend from the lower surface of the support for mounting the support within the hollow interior of the grid and second means also extend from the lower surface of the support for mounting the cathode.

7 Claims, 2 Drawing Figures CATHODE-GRID ASSEMBLY FOR A CATHODE RAY TUBE BACKGROUND OF THE INVENTION This invention relates to cathode ray tube cathodes and more particularly to a grid-cathode assembly for use with cathode ray tubes. Cathode ray tube cathodes of a current design comprise a cylindrical cathode which is welded to a heavy massive metallic eyelet which is in turn welded to a cathode support which is embedded into glass beads which align and maintain the cathode and several other grids. Such a cathode system is forced to utilize several long connections for supporting the grid and cathode and permits possible movement between these two elements. Prior art suggestions have also employed a cathode mounted within the cup shaped Gl grid of an electron gun. Such systems usually employed a ceramic disc having a plurality of metal rings brazed thereto. Spacers were also provided for positioning the ceramic disc within the GI. Such assemblies were expensive because of the machined ceramic disc and because of the necessity of brazing or using glass to metal sealing elements to at tach the metal components to the ceramic disc. It would be at an advance in the art if a simple, rugged and economical cathode structure could be provided.

OBJECTS AND SUMMARY OF THE INVENTION It is. therefore. an object of this invention to obviate the disadvantages of the prior art.

It is another object of this invention to enhance cathode mounting.

Yet another object of the invention is the provision of a simple, yet rugged and economical cathode support.

These objects are accomplished in one aspect of the invention with the provision of a cathode-grid assembly for a cathode ray tube which comprises a substantially cup shaped grid having a closed end containing a sub stantially centrally located aperture and a projecting contiguous side wall. The closed end and side wall de' fine a hollow interior. A cathode and a catohde support are positioned within the hollow interior and firmly and ruggedly affixed thereto. The cathode comprises a hol low metallic sleeve closed at one end by a cathode cap the outermost surface of which contains an electron emissive material. The cathode support comprises an electrically insulating member of a size to fit within the hollow interior of the grid and which has upper and lower surfaces. A substantially centrally located cathode receiving aperture interconnects the upper and lower surfaces. First means extend from the lower surface for mounting the support within the hollow interior of the grid and second means also extend from the lower surface of the support for mounting the cathode. This structure is rugged and simple and obviates the disadwmtages of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational sectional view shown in sirnplified form of the cathode-grid assembly of the invention; and

FIG. 2 is a plan view of the cathode-grid assembly shown in FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in conjunction with the abovedeseribed drawings.

Referring now to the drawings with greater particularity. there is shown in FIG. 1 a cathode-grid assembly 10 for a cathode ray tube. The cathode-grid assembly 10 comprises a substantially cup shaped grid 12 having a closed end 14 and a projecting contiguous side wall 16. A substantially centrally located aperture 18 is pro vided in closed end 14. The closed end 14 and contiguous wall 16 define a hollow interior 20. Positioned within the hollow interior 20 are a cathode 22 and a cathode support 24. The cathode comprises a hollow metallic sleeve 26 closed at one end by a cathode cap 28. The outermost surface of cap 28 contains an elec tron emissive material 30. The cathode support 24 is comprised of an electrically insulating member 32 of a suitable material such as glass. The electrically insulating member 32 is of a size to fit within the hollow interior and it has upper and

lower surfaces

34 and 36 respectively. A centrally located cathode aperture 38 is provided which interconnects the upper and lower surfaces. A first means 40 extends from the lower surface 36 of insulating member 32 to provide for mounting of the support 32 within the hollow interior 20 of grid 12. Also projecting from the bottom surface 36 are second means 42 for mounting the cathode 22.

The first means 40 comprises a plurality of rodlike metal elements 44 which have one end inserted and firmly affixed in electrically insulating member 32 and which project longitudinally therefrom along the longitudinal axis of the cathode and outwardly therefrom away from the longitudinal axis to provide a terminal portion 46 which attaches to the inside of the grid 12. By referring to FIG. 2 it will be seen that there are at least three rodlike metallic elements 44 and that they are substantially equidistantly spaced apart.

The second means 42 also comprises a plurality of rodlike members 48 which also have one end mounted within electrically insulating member 32 and which extend longitudinally therefrom along the longitudinal axis of the cathode and have a terminal portion 50 formed to extend inwardly toward the longitudinal axis of the cathode. The terminal portion 50 of the rodlike elements 48 is flattened to provide an attaching surface for the bell shaped bottom portion 52 of cathode 22.

Again. referring to FIG. 2, it will be seen that the rodlike elements 48 of second means 42 are also at least three in number and are substantially equidistantly spaced apart. Further, it will be seen that each of the rodlike elements 48 of the second means 42 is positioned substantially equidistantly between two of the rodlike elements 44 of the first means 40.

It will be seen from the above that an extremely rugged yet simple cathode-grid assembly is provided. The electrically insulating member 32, being formed of glass and having the first and second support means inserted therein allows that this structure can be fabricated on conventional electron tube stem making equipment. The cathode structure remains the same as that normally used with the prior art eyelet construction and thus further contributes to the low cost of the 3 device. No changes are necessary in the grid [2 which can be a conventional Gl assemblyv Because the cath ode 22 is mounted within the grid. one of the prime areas for misalignment is avoided.

While there have been shown what are at present considered to be the preferred embodiments of the in vention it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the inven tion as defined by the appended claims.

What is claimed is:

l. A cathode-grid assembly for a cathode ray tube comprising:

a substantially cup-shaped grid having a closed end containing a substantially centrally located aperture and a projecting contiguous side wall, said closed end and said side wall defining a hollow interim; and

a cathode and a cathode support positioned within said hollow interior;

said cathode comprising a hollow metallic sleeve closed at one end by a cathode cap the outermost surface of which contains an electron emissive material;

said cathode support comprising an electrically insulating member of a size to fit within said hollow interior and having upper and lower surfaces;

a substantially centrally located cathode aperture in- 4 terconnecting said upper and lower surfaces and first and second means extending from said lower surface for respectively mounting said support within said hollow interior and for mounting said cathode.

2. The assembly of claim 1 wherein said first means for mounting said support comprises:

a plurality of rod-like metallic elements inserted in said support and extending longitudinally and outwardly therefrom.

3. The assembly of claim 1 wherein said second means for mounting said cathode comprises:

a plurality of rod-like metallic elements inserted in said support and extending longitudinally and inwardly therefrom.

4. The assembly of claim 3 wherein the terminal portion of said second means is flat.

5. The assembly of claim 2 wherein said rod-like elements of said first means are three in number and substantially equidistantly spaced.

6. The assembly of claim 3 wherein said rod-like ele ments of said second means are three in number and substantially equidistantly spaced.

7. The assembly of claim 6 wherein each of said rodlike elements of said second means is positioned substantially equidistantly between two of said rod-like el' ements of said first means.

Claims

1. A cathode-grid assembly for a cathode ray tube comprising: a substantially cup-shaped grid having a closed end containing a substantially centrally located aperture and a projecting contiguous side wall, said closed end and said side wall defining a hollow interior; and a cathode and a cathode support positioned within said hollow interior; said cathode comprising a hollow metallic sleeve closed at one end by a cathode cap the outermost surface of which contains an electron emissive material; said cathode support comprising an electrically insulating member of a size to fit within said hollow interior and having upper and lower surfaces; a substantially centrally located cathode aperture interconnecting said upper and lower surfaces and first and second means extending from said lower surface for respectively mounting said support within said hollow interior and for mounting said cathode.

2. The assembly of claim 1 wherein said first means for mounting said support comprises: a plurality of rod-like metallic elements inserted in said support and extending longitudinally and outwardly therefrom.

3. The assembly of claim 1 wherein said second means for mounting said cathode comprises: a plurality of rod-like metallic elements inserted in said support and extending longitudinally and inwardly therefrom.

6. The assembly of claim 3 wherein said rod-like elements of said second means are three in number and substantially equidistantly spaced.

7. The assembly of claim 6 wherein each of said rod-like elements of said second means is positioned substantially equidistantly between two of said rod-like elements of said first means.