Information
-
Patent Grant
-
6246164
-
Patent Number
6,246,164
-
Date Filed
Thursday, April 1, 199925 years ago
-
Date Issued
Tuesday, June 12, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Patel; Nimeshkumar D.
- Hopper; Todd Reed
Agents
- Tripoli; Joseph S.
- Irlbeck; Dennis H.
-
CPC
-
US Classifications
Field of Search
US
- 313 402
- 313 407
- 313 404
- 313 405
-
International Classifications
-
Abstract
A color picture tube has a tensioned mask supported by a support frame mounted within said tube. The mask has a significantly lower coeffiecient of thermal expansion than the frame. Intermediary members are located between the mask and the frame. The intermediary members are of a material similar to that of the mask. Each of the members is attached to the frame at a single location and the mask is attached to edges of the intermediary members. Further included are guides for holding the intermediary members to the frame while permitting expansion of the frame relative to the intermediary members.
Description
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 tension 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, 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 low expansion materials. Therefore, it is desirable to use the combination of a low expansion tension mask with a higher expansion support frame, and to provide 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 tensioned mask supported by a support frame mounted within the tube. The mask has a significantly lower coeffiecient of thermal expansion than the frame. Intermediary members are located between the mask and the frame. The intermediate members are of a material similar to that of the mask. Each of the intermediate members is attached to the frame at a single location, and the mask is attached to edges of the intermediate members. Further included are guides for holding the intermediate members to the frame, while permitting expansion of the frame relative to the intermediary members.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1
is a side view, partly in axial section, of a color picture tube embodying the invention.
FIG. 2
is a perspective view of a tension mask-frame assembly.
FIG. 3
is a partial perspective view of the mask-frame assembly of FIG.
2
.
FIG. 4
is a cross-sectional view of the mask-frame assembly taken at line
4
—
4
of FIG.
2
.
FIG. 5
is a front view of the mask-frame assembly taken at line
5
—
5
of FIG.
2
.
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 funnel
15
. The funnel
15
has an internal conductive coating (not shown) that extends from an anode button
16
toward the panel
12
and 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 tension mask
24
is removably mounted in predetermined spaced relation to the screen
22
. 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 tension mask
24
, as shown in
FIGS. 2 and 3
, is attached to a peripheral frame
28
that includes two long sides
32
and
34
, and two short sides
36
and
38
. The two long sides
32
and
34
of the frame parallel a central major axis, X, of the tube; and the two short sides
36
and
38
parallel a central minor axis, Y, of the tube. The tension mask
24
includes an apertured portion that contains a plurality of metal strips
39
having a multiplicity of elongated slits
41
therebetween that parallel the minor axis of the mask. Each slit
41
extends between the two long sides
32
and
34
of the mask
24
.
As shown in greater detail in
FIG. 3
, each of the two long sides
32
and
34
(not shown) of the frame
28
includes a rigid section
40
and a compliant section
42
cantilevered from the rigid section. The rigid sections
40
are hollow tubes, and the compliant sections
42
are metal plates. The compliant sections
42
may 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
36
and
38
(not shown) has an L-shaped cross-section upper portion
44
parallel to and separated from a flat bar-shaped lower portion
46
.
Attached to each compliant section
42
is a intermediary member
48
, as shown in
FIGS. 3
,
4
and
5
. Each intermediary member
48
extends the length of a long side,
32
and
34
, and overlaps a compliant section
42
. The intermediary members
48
are welded to the compliant sections at a single central location
50
. The intermediary members
48
are of a material that has a coefficient of thermal expansion similar to that of the mask
24
. Therefore, changes of temperature will have little effect on the position of the mask
24
relative to the intermediary members
48
. The two ends,
52
and
54
of the intermediary members
48
are held to the compliant sections
42
by two clips,
56
and
58
, respectively, that extend outwardly from the compliant section
42
. The clips
56
and
58
serve as guides that hold the intermediary member
48
to prevent rotation of the member around its weld location
50
, while permitting longitudinal movement of the compliant section
42
, caused by its greater expansion during tube operation, relative to the intermediary member
48
. The clips
56
and
58
either may be formed by cutouts in the frame, as shown in
FIGS. 3
,
4
and
5
, or may be separate parts (not shown) that are welded to the frame. The two long sides of the tension mask
24
are welded to the upper distal edges of the two parallel intermediary members
48
.
In one preferred embodiment, the rigid sections
40
of the long side members
32
and
34
are hollow square tubes of
4130
steel having a wall thickness of 0.175 cm. The thicknesses of the compliant sections
42
and intermediary members
48
are 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
42
are plates of 4130 stainless steel that are 0.157 cm thick. The two L-shaped upper portions
44
are preferably of CRS-1018 steel having a thickness of 0.318 cm. The two bar-shaped lower portions
46
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
44
. When the frame
28
is heated, the lower portions
46
expand more than do the upper portions
44
. The differential expansion between the lower portions
46
and the upper portions
44
relieves stress in the compliant sections
42
and intermediary members
48
, while also reducing tension in the mask
24
during high temperature processing. The tension mask
24
and intermediary members
48
, preferably, are all constructed out of Invar or similar material that has a relatively low coefficient of thermal expansion. In one embodiment the mask
24
is 0.1 mm (4 mils) thick and the intermediary member
48
is 0.3 cm thick.
Although the rigid sections
40
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
36
and
38
of the frame
28
have been shown as having L-shaped cross-sections, other preferred configurations may be used, such as C-shaped, triangular shaped or box-shaped.
Claims
- 1. A color picture tube having a tension mask supported by a support frame mounted within said tube, comprisingsaid mask having a significantly lower coeffiecient of thermal expansion than said frame, intermediary members located between said mask and said frame, said members being of a material similar to that of said mask, each of said members being attached to said frame at a single central location and said mask being attached to edges of said intermediary members, and guides for holding said intermediary members to said frame to permit expansion of said frame relative to said intermediary members.
- 2. The color picture tube as defined in claim 1, wherein said guides are clips that are formed in said frame.
- 3. The color picture tube as defined in claim 1, wherein said guides are clips that are welded to said frame.
- 4. The color picture tube as defined in claim 1, wherein said mask is made from Invar and said frame is made from steel.
- 5. The color picture tube as defined in claim 4, wherein said intermediary members are made from Invar.
US Referenced Citations (7)