Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
2000-02-16
2001-08-14
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S407000
Reexamination Certificate
active
06274974
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a shadow mask type color cathode ray tube, and more particularly to a shadow mask type color cathode ray tube provided with a shadow mask capable of being installed into the color cathode ray tube without causing curvature distortions or reduction in strength of the shadow mask by reducing curls occurring in the skirt portion thereof in press-forming the shadow mask.
Generally in assembling a shadow mask type color cathode ray tube, a skirt portion of the shadow mask formed by press-forming is fitted within a support frame, the shadow mask is affixed to the support frame by spot welding, and then the support frame is suspended within a panel portion of the color cathode ray tube such that the shadow mask is positioned adjacent to, but spaced from a phosphor film formed on the inner surface of a faceplate of the panel portion.
FIGS. 4A
to
4
C are respectively structural views showing an example of the shadow mask used for a conventional color cathode ray tube.
FIG. 4A
is a front view of the shadow mask,
FIG. 4B
is an enlarged fragmentary side view of an area in the vicinity of welds in the skirt portion thereof, and
FIG. 4C
is a sectional view of a region extending from an imperforate portion to the skirt portion. In
FIGS. 4A
to
4
C, reference numeral
41
designates a shadow mask;
42
is an apertured portion;
43
is an imperforate portion; and
44
is a skirt portion, and x marks indicate welds.
The shadow mask
41
has a curved apertured portion
42
having a multiplicity of electron-transmissive apertures, a curved imperforate portion
43
surrounding and integral with the apertured portion
42
and a skirt portion
44
bent back from a periphery of the curved imperforate portion
43
, and is usually integrally formed by press-forming a multi-apertured thin sheet-like metal blank.
In this case, the multi-apertured thin sheet-like metal blank is very thin and relatively weak in strength. Therefore, the press-formed shadow mask
41
is not always good in forming characteristics. Especially, the skirt portion
44
of the shadow mask
41
curls outwardly by a distance S from a straight line passing through a bend line between the imperforate portion
43
and the skirt portion
44
and parallel to the longitudinal axis of the cathode ray tube, in a region centering about the center of each side of the generally rectangular shadow mask
41
, as shown in FIG.
4
C.
The skirt portion
44
of the press-formed shadow mask
41
is fitted within or outside a support frame (not shown), and is welded and affixed to the support frame at a few points. As indicated in
FIG. 4B
by x marks, welds of the skirt portion
44
and the support frame are located two in the vicinity of the center of each of the long and short sides of the shadow mask
41
, and one at each of the four corners thereof, for example.
When the conventional shadow mask
41
is press-formed, occurrence of the curl S in the skirt portion
44
is unavoidable, and if the curl S is excessively large, it is an obstacle to fitting the skirt portion
44
into the support frame and welding the fitted portion thereof to the support frame, resulting in reduction of workability.
Further, when the skirt portion
44
of the conventional shadow mask
41
having the large curl S is forcibly fitted in the support frame, the stress applied to the skirt portion
44
is transmitted to the imperforate portion
43
and the apertured portion
42
, and distorts the curved contour of the apertured portion
42
of the shadow mask
41
, and as a result, the color selection property of the shadow mask
41
is degraded, and the strength of the shadow mask
41
is reduced.
SUMMARY OF THE INVENTION
The present invention solves these problems as noted above, and an object of the present invention is to provide a shadow mask type color cathode ray tube provided with a shadow mask having the workability improved in being affixed to the support frame and its curvature distortions prevented, by reducing the amount of curls in the skirt portion of the press-formed shadow mask.
For achieving the aforesaid object, a color cathode ray tube according to an embodiment of the present invention includes a generally rectangular shadow mask having a curved apertured portion having a multiplicity of electron-transmissive apertures, a curved imperforate portion surrounding and integral with the apertured portion and a skirt portion bent back from a periphery of the curved imperforate portion, and a generally rectangular support frame for suspending the shadow mask by spot welding the skirt portion thereto, within a panel portion of the color cathode ray tube; wherein the skirt portion is provided with a plurality of slits extending in a direction of a height of the skirt portion and a plurality of embossments extending in the direction of the height of the skirt portion, and the slits and the embossments are juxtaposed around a circumference of the skirt portion.
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Hagiwara Koji
Hosotani Nobuhiko
Ito Hiroshi
Ito Masahiro
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Patel Nimeshkumar D.
Williams Joseph
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