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US 4,047,778 AGranted
Apparatus for converting CRT cathodes
AssigneeHewlett-Packard Company
InventorJulius A. Csaki
Life of this patent
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Abstract
Vacuum pump exhaust manifold pressure is employed to control the conversion voltage applied during a CRT conversion process for enabling conversion of CRT cathodes in a nearly constant vacuum environment.
Claims7
Apparatus for converting a cathode of a cathode ray tube (CRT) during the manufacture of the CRT, the apparatus comprising:
- power supply means for applying a conversion voltage to a CRT filament associated with the CRT cathode to be converted;
- vacuum pump means for establishing a vacuum condition within the CRT;
- vacuum sensing means for detecting the vacuum level within the CRT during conversion;
- and
- logic means coupled to said power supply means and vacuum sensing means, said logic means being responsive to said vacuum sensing means for causing said conversion voltage to steadily increase from a first predetermined voltage level to a second predetermined voltage level so long as the vacuum level within the CRT is greater than a first predetermined vacuum level, said logic means being responsive to said vacuum sensing means for causing said conversion voltage to steadily decrease from the most recently achieved voltage level toward said first predetermined voltage level if the vacuum level within the CRT falls below a second predetermined vacuum level that is lower than said first predetermined vacuum level, said logic means being responsive to said vacuum sensing means for preventing any increase or decrease in the most recently achieved conversion voltage so long as the vacuum level within the CRT is between said first and second predetermined vacuum levels.
2 more elements
A method for converting a cathode of a cathode ray tube (CRT) during the manufacture of the CRT, the method comprising:
- establishing a vacuum condition within the CRT;
- applying a conversion voltage to a CRT filament associated with the CRT cathode to be converted, the conversion voltage steadily increasing from a first predetermined voltage level to a second predetermined voltage level so long as the vacuum level within the CRT is greater than a first predetermined vacuum level;
- applying a conversion voltage to the CRT filament associated with the CRT cathode to be converted, the conversion voltage steadily decreasing from the most recently achieved voltage level toward said first predetermined voltage level if the vacuum level within the CRT falls below a second predetermined vacuum level that is lower than said first predetermined vacuum level;
- applying a conversion voltage to the CRT filament associated with the CRT cathode to be converted, the conversion voltage being a constant voltage equal to the most recently achieved voltage level so long as the vacuum level within the CRT is between said first and second predetermined vacuum levels.
1 more element
Dependencies are inferred from the claim text.