CATHODE-RAY TUBE HAVING IMPROVED 16 X 9 ASPECT RATIO FACEPLATE PANEL

ECRAN CATHODIQUE AVEC DALLE DE VERRE PRESENTANT UN RAPPORT HAUTEUR/LARGEUR 16 X 9 AMELIORE

English Abstract

The present invention provides an improvement in a
cathode-ray tube that includes a rectangular faceplate panel having
two peripheral long sides and two peripheral short sides, wherein
the ratio of length of the long sides to the length of the short sides is
approximately 16/9. The tube includes a major axis which parallels
the two long sides and a minor axis which parallels the two short
sides. A rectangular viewing screen is located on an inner surface of
the faceplate panel. The improvement comprises the long sides of
the panel having a radius of curvature in a plane of the major and
minor axes that is about 7 to 10 times longer than a diagonal
dimension of the viewing screen, and the ratio of the radius of
curvature of the long sides to the radius of curvature of the short
sides being in the range of about 1.6 to 1.9.

Claims

7
CLAIMS
1. A cathode-ray tube including a rectangular
faceplate panel having two long sides and two short sides, the
ratio of the length of said long sides to the length of said short
sides being approximately 16/9, said tube including a major axis
which parallels said two long sides and a minor axis which
parallels said short sides, and said tube including a rectangular
viewing screen on an inner surface of said faceplate panel,
comprising
said long sides of said panel having a radius of
curvature in a plane of said major and minor axes that is about
7.5 to 8.5 times longer than a diagonal dimension of said viewing
screen, and the ratio of the radius of curvature of said long sides
to the radius of curvature of said short sides being in the range of
about 1.6 to 1.9.
2. The tube as defined in claim 1, wherein when
the diagonal dimension of said viewing screen is about 762 mm,
said long sides of said panel have a radius of curvature of
approximately 6450 mm and said short sides have a radius of
curvature of approximately 3504 mm.
3. The tube as defined in claim 1, wherein the ratio
of said long sides to said diagonal is about 8.5 and the ratio of the
radius of curvature of said long sides to the radius of curvature of
said short sides is about 1.8.
4. The tube as defined in claim 1, wherein when
the diagonal dimension of said viewing screen is about 660 mm,
said long sides of said panel have a radius of curvature of
approximately 5001 mm and said short sides have a radius of
curvature of approximately 2999 mm.

8
5. The tube as defined in claim 1, wherein the ratio
of said long sides to said diagonal is about 7.6 and the ratio of the
radius of curvature of said long sides to the radius of curvature of
said short sides is about 1.7.

Description

1 RCA 86,034
CATHODE-RAY TUBE HAVING IMPROVED
16 X 9 ASPECT RATIO FACEPLATE PANEL
This invention relates to cathode-ray tubes (CRT's) and,
particularly, to ehe peripheral shapes of the faceplate panels of such
tubes having approximately 16 x 9 rectangular aspect ratios.
Back~:round Of The Invention
Until now, commercial television cathode-ray tubes have
had viewing screens and panels with 4 x 3 aspect ratios. (Aspect
ratios are given in width or horizontal dimension to height or vertical
dimension.) In the near future, however, cathode-ray tubes having
wider aspect ratios will be required when higher definition television
systems are introduced into commercial television. Most motion
pictures are filmed in an approximate aspect ratio of 22 x 9.
However, since a cathode-ray tube having a 22 x 9 aspect ratio
would be excessively heavy for its size, the tube industry has
standardized on a lower 16 x 9 aspect ratio, as a compromise for the
future higher definition systems.
The early development tubes that have been constructed
2 0 with the 16 x 9 aspect ratio have had faceplate panels that included
peripheral sides with relatively large curvature. The purpose of
curving the peripheral sides is to provide the panel with sufficient
strength to withstand atmospheric pressure when the tube is
evacuated. The drawback of a panel having sides with large
2 5 peripheral side curvature is that additional space must be provided
in a television receiver cabinet to accommodate the cathode-ray
tube. However, receiver designers would like to keep the size of the
cabinets as small and as light as possible. Making a tube with a

RCA 86,034
~~3~~3~~
panel having straight sides would provide a tube with minimum
dimensions, but would require an undesirable increase in glass
thickness, and thus also in tube weight. Therefore, there is a need
for a cathode-ray tube design that provides a compromise of
S minimized height and width of the tube panel and minimized tube
weight.
Summary Of The Invention
The present invention provides an improvement in a
cathode-ray tube that includes a rectangular faceplate panel having
two peripheral long sides and two peripheral short sides, wherein
the ratio of length of the long sides to the length of the short sides is
approximately 16/9. The tube includes a major axis which parallels
the two long sides and a minor axis which parallels the two short
sides. A rectangular viewing screen is located on an inner surface of
the faceplate panel. The improvement comprises the long sides of
the panel having a radius of curvature in a plane of the major and
minor axes that is about 7 to 10 times longer than a diagonal
dimension of the viewing screen, and the ratio of the radius of
curvature of the long sides to the radius of curvature of the short
2 0 sides being in the range of about 1.6 to 1.9.
Brief Description Of The Drawings
FIGURE 1 is a side view, partly in axial section, of a shadow
mask color picture tube incorporating one embodiment of the
present invention.
2 5 FIGURE 2 is a plan view of the backside of the faceplate of
the tube of FIGURE 1.

RCA 86,034
~~398~
FIGURE 3 is a composite plan view of the outer periphery of
quadrants of a faceplate panel showing a straight side, a prior art
curved side and a novel curved side.
Detailed Description Of The Preferred Embodiments
FIGURE 1 shows a rectangular color picture tube 10 having a
glass bulb or envelope 11 comprising a rectangular faceplate panel
12 and a tubular neck 14 connected by a rectangular funnel 15. The
funnel 15 has an internal conductive coating (not shown) that
extends from an anode button 16 to the neck 14. The panel 12
comprises a rectangular viewing faceplate 18 and a peripheral flange
or sidewall 20 which is sealed to the funnel 15 by a glass frit 17. A
three-color phosphor screen 22 is carried by the inner surface of the
faceplate 18. The screen 22 preferably is a line screen with the
phosphor lines arranged in triads, each triad including a phosphor
1 5 line of each of the three colors. Alternatively, the screen can be a dot
screen, and it may or may not include a light-absorbing matrix. A
mufti-apertured color selection electrode or shadow mask 24 is
removably mounted in predetermined spaced relation to the screen
22. An electron gun 26, shown schematically by dashed lines in
2 0 FIGURE 1, is centrally mounted within the neck 14 to generate and
direct three electron beams 28 along convergent paths through the
mask 24 to the screen 22.
The tube of FIGURE 1 is designed to be used with an
external magnetic deflection yoke, such as the yoke 30 shown in the
2 5 neighborhood of the funnel-to-neck junction. When activated, the
yoke 30 subjects the three beams 28 to magnetic fields which cause
the beams to scan horizontally and vertically in a rectangular raster

4 RCA 86,034
over the screen 22. The initial plane of deflection (at zero deflection)
is at about the middle of the yoke 30. Because of fringe fields, the
zone of deflection of the tube extends axially from the yoke 30 into
the region of the gun 26. For simplicity, the actual curvatures of the
deflected beam paths in the deflection zone are not shown in
FIGURE 1.
As shown in FIGURE 2, the rectangular faceplate panel 12
includes two orthogonal axes, a major axis X and a minor axis Y, and
two diagonals D. The two long sides, L, of the periphery of the
faceplate panel 12 substantially parallel the major axis X, and the
two short sides, S, substantially parallel the minor axis Y. Preferably,
both the long and short sides of the faceplate are curved in the X, Y
and D plane, with the ratio of the radius of curvature of a long side to
the radius of curvature of a short side being in the range of about 1.6
1 5 to 1.9. Furthermore, the ratio of the radius of curvature of a long
side to the diagonal dimension of the screen is in the range of about
7 to 10. These ranges represent an optimum design for a tube
having a 16 x 9 aspect ratio.
Table I presents dimensions and ratios for three 16 x 9
2 0 faceplate panels that are within the scope of the present invention
[(1) to 3)], two 16 x 9 faceplate panels that are indicative of the prior
art [(4) and (5)] and three 4 x 3 faceplate panels [(6) to (8)], for
comparison purposes.

RCA 86,034
TABLE I
Screen Long SideShort Side
Tube DiagonalRadius Radius Long/ShortLong/Diag.
5 Tune (mm) (mm) (mm) Radius Ratio
Ratio
New
16x9
( 1 8 6 3 7691.06 4280.33 1.797 8.906
) . 6
(2) 7 6 2 6450.15 3504.73 1.840 8.465
1 (31 660 4 5001 21 2999 41 1 667 7 573
0
Prior
16x9
(4) 863.6 3003 2683 1.119 3.477
(5) 762 2652 2370 1 119 3 480
Prior
(6) 8 8 9 5522 5434 1.016 6.211
(7) 787.4 4837.39 4703.71 1.028 6.143
( 8 6 8 5 5408.96 3941.42 1.372 7.887
) . 8
FIGURE 3 illustrates a composite of the long side curvatures
for three types of 16 by 9 aspect ratio faceplate panels: a panel with
straight sides 32, a prior art panel with greater curved sides 34 and
a novel panel with lesser curved sides 36. From an aesthetics and
2 5 space point of view, the panel having the straight sides 32 is the
most desirable. However, the stresses in the panel with straight
sides are relatively high, thereby necessitating a substantial increase
in the thickness and weight of the panel over that of a prior art
panel. Although the prior art panel design permits use of thinner
3 0 and lighter glass, the greater curvature of the sides of the panel
requires a larger space in a television receiver cabinet, thereby
resulting in a bulkier product. A faceplate panel constructed in
accordance with the present invention requires less room in a

6 RCA 86,034
~~ s~~~~
receiver cabinet and is slightly lighter in weight than the prior art
panel. Finite element calculations performed on the novel panel
indicate that the stresses within the glass of the novel panel are
higher than that found in the prior art panels, but that when the
S novel panels are assembled into tubes with implosion protection
means thereon, the tubes with the novel panels show no increase in
implosion possibility over the prior art tubes.

Representative Drawing