Electric lamp and discharge devices – Cathode ray tube – Ray generating or control
Reexamination Certificate
2000-03-24
2002-04-16
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Ray generating or control
C313S447000, C313S309000
Reexamination Certificate
active
06373182
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to electron guns for devices such as cathode ray tubes (CRTs). More particularly, apparatus and method that may use modified parts of conventional electron guns are provided for mounting field emission devices.
2. Description of Related Art
A conventional electron gun uses a thermionic emitter as the source of electrons.
FIG. 1
illustrates a common configuration of the lower parts of an electron gun using a thermionic emitter. Parts of an electron gun having a cathode and two grids are generally shown at
10
. Both grids, along with other grids, are normally “beaded” into a structure that makes up the entire electron gun. Filament
12
is used to heat emissive coating
14
to cause electron emission. Cathode cap
16
, attached to cathode shank
18
, supports emissive coating
14
(usually a combination of one or more of barium, strontium or calcium carbonates, which are converted to oxides in a CRT). Cathode shank
18
is normally welded to interface ring
20
. Interface ring
20
may be formed integral in ceramic cathode mount
22
. Ceramic cathode mount
22
is free to slide in grid
24
but is fastened in place by welding during final electron gun assembly. Grid
24
(G
1
) and Grid
26
(G
2
) are used to focus and accelerate the electrons produced by emissive coating
14
. The grids are biased electrically in a way to create a source of electrons that can be further focused and modulated by other grids to satisfy CRT requirements.
The technology to allow replacement of cathodes based on thermionic emission with cold cathodes based on field emission of electrons (Field Emission Devices or FEDs) has been developing in recent years. The emission of electrons from cold cathodes may occur from microtips that are fabricated from molybdenum, silicon or, in very recent years, carbon-based materials. It has been demonstrated that the carbon-based material or diamond-like material can be monolithically integrated with gated electrodes in a self-aligned structure, using integrated circuit fabrication techniques (“Advanced CVD Diamond Microtip Devices for Extreme Applications,” MAT. RES. SOC. SYMP. PROC., Vol. 509 (1998)). The use of field emission devices with the extraction gate built-in eliminates the need for two of the electrodes in an electron gun built on thermionic emission, G
1
and G
2
of
FIG. 1
Elimination of these electrodes simplifies the gun and also reduces its length. The application of the integrated carbon-like cathode and electrodes into an electron gun has been described in a pending and commonly assigned patent application entitled “Compact Field Emission Electron Gun and Focus Lens,” filed Jul. 19, 1999, Ser. No. 09/356,851, with named inventors Rich Gorski and Keith D. Jamison, which is incorporated herein by reference. A segmented cathode has been disclosed in pending and commonly assigned patent application “Segmented Gate Drive for Dynamic Beam Correction in Field Emission Cathodes,” filed Dec. 31, 19999, Ser. No. 09/476,051, with named inventors Keith D. Jamison and Donald E. Patterson, which is incorporated herein by reference. A package structure for mounting a field emitting cathode into an electron gun is described in a pending and commonly assigned patent application entitled “Package Structure for Mounting a Field Emitting Device in an Electron Gun”, filed Jan. 28, 2000, Ser. No. 09/493,379, with named inventors Randolph D. Schueller, Kent R. Kalar and Anthony A. Kloba, which is incorporated herein by reference.
Structures for incorporating field emission cathodes into an electron gun are known. but these structures require either considerable re-engineering or replacement of the parts of electron guns using thermionic emitters or newly designed parts. The electron gun design changes and gun part tool modifications are both costly and time-consuming. The use of field emission devices (FEDs) as cathodes is new in the cathode ray tube (CRT) industry and demonstration of their benefits in a CRT using prior methods or apparatus would require costly and time-consuming electron gun design changes. Once the advantages of FEDs are demonstrated, these changes are expected to prove well worth the expense. What is needed is a structure and method that require minimal modification of the parts of already commercial electron guns that use thermionic emission, i.e., that do not require extensive gun design and part tooling changes, while serving all the requirements of FEDs. Use of the structure in a CRT should also allow minimum changes in electrical connections to the CRT.
BRIEF SUMMARY OF THE INVENTION
An electron gun structure for use of a field emission cathode having an integral extraction grid is provided. The structure includes a spring confined in a hollow member, which may be the grid (G
1
) of a conventional electron gun, that acts on a shank, which may be the cathode shank of a conventional electron gun, to press an electrical contact area around an emitting array against a second surface, which may be the grid (G
2
) of a conventional electron gun. The electrical contact area is electrically connected to the extraction grid of a field emission array. The grid may be integrally formed with the emitters of the array. The field emitting array is formed on a substrate and is preferably carbon-based. In another embodiment, a support plate is placed beneath the substrate to increase the mechanical contact area between the cathode cap and the FED substrate. In yet another embodiment, the cathode shank is cut off, which may reduce angular mounting errors in some applications.
REFERENCES:
patent: 4687964 (1987-08-01), Ebihara et al.
patent: 5877594 (1999-03-01), Miyano et al.
patent: 197 03 238 (1997-07-01), None
patent: 197 28 679 (1998-01-01), None
patent: 0 772 218 (1997-05-01), None
patent: 0 944 107 (1999-09-01), None
Patterson, D. E. et al., “Advanced CVD Diamond Microtip Devices for Extreme Applications,” Materials Research Society Symposium Proceedings, vol. 509, pp. 65-75, XP001006112 (1998).
D.E. Patterson, et al.,Advanced CVD Diamond Microtip Devices for Extreme Applications, Mat. Res. Soc. Symp. Proc. vol. 59 (1998).
Delguzzi David A.
Jamison Keith D.
Kalar Kent R.
Kloba Anthony A.
Patterson Donald E.
Clove Thelma Sheree
Extreme Devices Inc.
Patel Nimeshkumar D.
LandOfFree
Mounting for cathode in an electron gun does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mounting for cathode in an electron gun, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mounting for cathode in an electron gun will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2910465