Color picture tube having a tensioned mask-support frame assembly

An improved color picture tube has a tensioned mask and support frame assembly. Each of the mask and the support frame is rectangular and has two long sides that parallel a central major axis thereof and two short sides that parallel a central minor axis thereof. The improvement comprises the frame including two first members, paralleling the major axis, and two second members, attached to the ends of said first members, paralleling the minor axis. Each of the second members includes a pinched section that elongates it.

This invention relates to color picture tubes having masks, and 
particularly to a tube with a mask-frame assembly having a tensioned mask 
that is attached to a support frame. 
BACKGROUND OF THE INVENTION 
A color picture tube includes an electron gun for generating and directing 
three electron beams to a 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 contoured to somewhat 
parallel the inner surface of the tube faceplate. A focus mask comprises 
dual sets of conductive lines that are perpendicular to each other and 
usually separated by an insulative layer. 
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, and to simplify the process of 
maintaining tension in the mask following high temperature processing. 
SUMMARY OF THE INVENTION 
The present invention provides an improvement in a color picture tube 
having a tensioned mask and support frame assembly. Each of the mask and 
the support frame is rectangular and has two long sides that parallel a 
central major axis thereof and two short sides that parallel a central 
minor axis thereof. The improvement comprises the frame including two 
first members paralleling the major axis and two second members, attached 
to the ends of the first members, paralleling the minor axis. Each of the 
second members includes a pinched section that elongates the member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a color picture tube 10 having a glass 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 substantially cylindrical 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 is a line screen with the 
phosphor lines arranged in triads, each triad including a phosphor line of 
each of the three colors. A color selection electrode or tensioned mask 24 
is removably mounted in predetermined spaced relation to the screen 22. 
The tensioned mask 24 may be either a shadow mask or a focus mask. An 
electron gun 26, shown schematically by dashed lines in FIG. 1, is 
centrally mounted within the neck 14 to generate and direct three inline 
electron beams, a center beam and two side or outer beams, along 
convergent paths through the mask 24 to the screen 22. 
The tube 10 is designed to be used with an external magnetic deflection 
yoke, such as the yoke 30 shown in the neighborhood of the funnel-to-neck 
junction. When activated, the yoke 30 subjects the three beams to magnetic 
fields which cause the beams to scan horizontally and vertically in a 
rectangular raster over the screen 22. 
The tensioned mask, shown in the form of a tensioned shadow mask 24 in FIG. 
2, includes two long sides 32 and 34, and two short sides 36 and 38. The 
two long sides 32 and 34 of the mask parallel a central major axis, X, of 
the mask; and the two short sides 36 and 38 parallel a central minor axis, 
Y, of the mask. The tensioned shadow mask 24 of FIG. 2 includes an 
apertured portion that contains a multiplicity of elongated slits that 
parallel the minor axis of the mask. Each slit extends from near one long 
side of the mask to near the other long side. Another form of tensioned 
mask is a tensioned focus mask 24', shown in FIG. 3. The tensioned focus 
mask 24' includes dual sets of conductive lines 25 and 27 that are 
perpendicular to each other and separated by an insulative layer (not 
shown). 
A frame 40, for use with either the tensioned shadow mask 24 or the 
tensioned focus mask 24', is shown in FIG. 4. The frame 40 includes four 
sides: two long sides 42 and 44, substantially paralleling the major axis 
X of the tube, and two short sides 46 and 48, paralleling the minor axis Y 
of the tube. As shown in greater detail in FIGS. 5 and 6, each of the two 
sides 42 and 44 includes a rigid section 50 and a compliant section 52 
cantilevered from the rigid section. The rigid sections 50 are hollow 
tubes, and the compliant sections 52 are metal plates. The compliant 
sections 52 vary in height from the center of each section longitudinally 
to the ends of the sections, to permit the best tension compliance over 
the mask. Each of the short sides 46 and 48 has an L-shaped cross-section 
upper portion 60 parallel to and separated from a flat bar-shaped lower 
portion 62. The two long sides of the tension mask 24 are welded to the 
distal ends of the compliant sections 52. Each short side upper portion 60 
is welded at each end to the rigid sections 50 of the longs sides at 
sufficient points 64 to assure that it is rigidly attached. The short side 
lower portions 62 are firmly welded to the bottoms of both of the rigid 
sections 50. The upper portion has two flanges, 66 and 68, at a right 
angle to each other. The flange 66 is perpendicular to the central 
longitudinal Z axis, and the flange 68 parallels the Z axis. Preferably, 
at one end of the upper portion 60, the flange 66 extends beyond the 
flange 68, so that, at that one end, only the flange 66 contacts and is 
welded to a rigid section 50. The part 70 of the flange 66 that extends 
beyond the flange 68 provides a location that can be used to increase the 
tension on the mask 24, which may have been decreased by exposures to high 
temperatures during processing of the mask-frame assembly. Following such 
processing, the part 70 is stretched by some mechanical means, such as a 
preferred method of pinching the part 70 with a suitable pinching device. 
The width and depth of the pinch controls the elongation of the part 70. 
Additionally, the pinch may be in both surfaces of the part 70, as shown 
in FIG. 6 by the pinch 72, or confined to one surface. Also, the part 70 
may be included in both ends of the flange 66, or in an intermediate 
portion thereof. The mask-frame assembly with the part 70 pinched, is 
shown in FIG. 6. For present purposes, pinching is the pressing against a 
metal to compress and elongate the metal. 
In one preferred embodiment, the rigid sections 50 of the long side members 
42 and 44 are hollow square tubes of 4130 steel having a wall thickness of 
0.175 cm. The thickness of the compliant sections 52 is determined by 
considering mask thickness, the flexibility of the total mask-frame 
assembly and the desired warp misregistration limits. In a further 
preferred embodiment, the compliant sections 52 are plates of 4130 
stainless steel that are 0.157 cm thick. The compliant sections 52 also 
can be bimetal plates, such as of stainless steel/stainless steel or 
stainless steel/Invar. The two upper portions 60 are preferably of 
CRS-1018 steel having a thickness of 0.318 cm. The two lower portions 62 
are preferably of 300 Series stainless steel, which has a different 
coefficient of thermal expansion than does the CRS-1018 steel of the upper 
portions 60. When the frame 40 is heated, the lower portions 62 expand 
more than do the upper portions 60. Because of the flexible connections 
between the straight and curved members, the differential expansion 
between the lower portions 62 and the upper portions 60 relieves stress in 
the compliant sections 52 and tension in the mask 24 during high 
temperature processing. 
Although the rigid sections 50 have been shown as hollow square tubes, 
other preferred configurations, such as those having L-shaped, C-shaped or 
triangular-shaped cross-sections, are also possible for these sections. 
Furthermore, although the short sides 46 and 48 have been shown as having 
L-shaped cross-sections, other preferred configurations may be C-shaped, 
triangular shaped or box-shaped.