Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
1999-04-01
2001-05-01
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S402000
Reexamination Certificate
active
06225736
ABSTRACT:
This invention relates to color picture tubes having tension masks, and particularly to a tube having means for connecting a tension mask, that is made of a material having a relatively low coefficient of thermal expansion material, to a support frame, that has a significantly higher coefficient of thermal expansion.
BACKGROUND OF THE INVENTION
A color picture tube includes an electron gun for generating and directing three electron beams to the screen of the tube. The screen is located on the inner surface of a faceplate of the tube and is made up of an array of elements of three different color emitting phosphors. A color selection electrode, which may be either a shadow mask or a focus mask, is interposed between the gun and the screen to permit each electron beam to strike only the phosphor elements associated with that beam. A shadow mask is a thin sheet of metal, such as steel, that is usually contoured to somewhat parallel the inner surface of the tube faceplate.
One type of color picture tube has a tensioned shadow mask mounted within a faceplate panel thereof. In order to maintain the tension on the mask, the mask must be attached to a relatively massive support frame. Although such tubes have found wide consumer acceptance, there is still a need for further improvement in tube types to reduce the weight and cost of the mask-frame assemblies in such tubes.
It has been suggested that a lighter frame could be used in a tension mask tube if the required tension on a mask is reduced. One way to reduce the required mask tension is to make the mask from a material having a low coefficient of thermal expansion. However, a mask from such material would require a support frame of a material having a similar coefficient of thermal expansion to prevent any mismatch of expansions during thermal processing that is required for tube manufacturing, and during tube operation. Because the metal materials that have low coefficients of thermal expansion are relatively expensive, it is relatively costly to make both the mask and frame out of identical or similar materials. Therefore, it is desirable to use the combination of a low expansion tension mask with a higher expansion support frame. The present invention provides a solution to the problem that exists when there is a substantial mismatch in coefficients of thermal expansion between a tension mask and its support frame.
SUMMARY OF THE INVENTION
The present invention provides an improvement in a color picture tube having a tension mask supported by a support frame mounted within the tube. The tension mask has a significantly lower coefficient of thermal expansion than that of the frame. The mask includes an active apertured portion formed by a plurality of parallel vertically extending strands, between which are elongated apertures through which electron beams pass during operation of the tube. Two opposite side border portions, outside the active apertured portion, have tie bars that extend between the vertical strands of the mask. The tie bars accommodate expansion of the frame, while substantially maintaining the positions of the vertical strands in the active portion of the mask.
REFERENCES:
patent: 3573528 (1971-04-01), Maeda
patent: 4973283 (1990-11-01), Adler et al.
patent: 5488263 (1996-01-01), Takemura et al.
patent: 0602620A1 (1994-06-01), None
patent: 0788132A2 (1997-08-01), None
patent: 2308223 (1997-06-01), None
patent: 2311165 (1997-09-01), None
patent: 59-203349 (1984-11-01), None
Patent Abstract of Japan, vol. 009, No. 065 (E-304), Mar. 26, 1985 & (Toshiba KK).
Irlbeck Dennis H.
Patel Vip
Thomson Licensing S.A.
Tripoli Joseph S.
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