Electric lamp and discharge devices – With electrode replacement means or demountable
Reexamination Certificate
1998-09-17
2001-06-26
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With electrode replacement means or demountable
C313S282000, C219S121140, C219S121120, C219S121270
Reexamination Certificate
active
06252339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electron beam projection systems and more particularly to methods and apparatus for replacement of electron beam projection system components such as electrodes, i.e. filaments, and cathodes.
2. Description of Related Art
U.S. Pat. No. 4,634,921 of Williams et al. for “Thermionic Cathode Heater” describes a cathode for producing and electron beam which includes a cathode heater comprising a straight wire inside a conducting circular cylinder. The cylinder in turn is located within a cathode which is heated by current through the straight wire flowing in one direction and then returning through the cylinder. The cathode is composed of a conductive material such as sintered tungsten.
U.S. Pat. No. 4,583,023 of Friedman et al. for “Electron Beam Heated Thermionic Cathode” describes an electron beam generator or the like initially heated by a suitable heating means such as an electrical hot plate to a temperature sufficient for low level electron emission from its rear surface. A sustainer voltage is applied between the cathode and the hot plate to draw electron flow of a “back electron beam” from the cathode to the hot plate through the space between them. The back electron beam heats the hot plate to a temperature sufficient to raise the temperature of the closely spaced cathode to the desired emission temperature. This heater process is ended at that point since the heating is used only initially until the desired emission temperature is reached.
SUMMARY OF THE INVENTION
In the past the electrodes which produced electron beams have included the terms “cathode” and “filament” which may have been used interchangeably. In the case of the present invention, the devices being employed include a filament which generates a primary electron beam which heats a cathode which produces a secondary high energy electron beam directed into the column of an electron beam projection system. The problem dealt with by this invention has to do with the replacement of components such as filaments in an electron beam column, when necessary, without requiring venting the system.
In accordance with this invention, a method and apparatus are provided which permit installing and removing an element such as an electron beam generating component such as a filament or cathode element module from an electron gun without having to remove the electron gun from the electron column. The feed-through connector is removed from the connector port in the gun and then the element module is removed from the connector port. Removal of the feedthrough element from the top of the gun provides easy access to the module. The element is replaced through an opening made accessible by removing the feedthrough element. Then the element is simply lifted out of the gun and the new element is placed into position. To facilitate quick connection, the element module is installed in the electron gun in a way that all electrical connections to the support plates are automatic.
In another aspect of this invention, a load-lock can be provided above the connector port to avoid venting into the gun. A bellows between the feedthrough element and the top of the load-lock chamber can facilitate removal of the feedthrough without exposure of the gun to ambient atmospheric gases.
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Jones II Graham S.
Nikon Corporation
Patel Nimeshkumar D.
Santiago Mariceli
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