Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
2000-04-17
2001-04-24
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Envelope
C313S318010, C313S318050
Reexamination Certificate
active
06222311
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cathode ray tube, and particularly to a cathode ray tube including a stem having a plurality of stem pins annularly arrayed, and sealed and extending therethrough and having glass mounds raised and surrounding the base of each of the stem pins on the side thereof supporting an electron gun, and a neck portion at one end thereof heat-sealed by the stem.
Generally, a color cathode ray tube known as a cathode ray tube emitting a plurality of electron beams has a vacuum envelope composed of a panel portion having a phosphor screen coated with a phosphor on the inner surface thereof and suspending a shadow mask therein closely spaced from the phosphor screen, a funnel portion connected to and tapered down from the panel portion, a neck portion connected. thereto, and a stem supporting an electron gun housed in the neck portion and fused to an open end of the neck portion.
The stem has a plurality of stem pins annularly arrayed and sealed and extending therethrough to support electrodes of the electron gun and introduce various signal voltages from an external circuit.
A deflection yoke is mounted exteriorly in a transition region between the funnel portion and the neck portion, and a plurality of electron beams modulated by video signals and emitted from the electron gun are deflected in two directions, i.e. horizontally and to thereby reproduce a visible image on the phosphor screen.
FIG. 7
is a schematic sectional view for explaining the schematic construction of a color cathode ray tube to which the present invention is applied. Reference numeral
13
designates stem pins,
14
a stem,
20
a panel portion,
21
a neck portion,
22
a funnel portion,
23
a phosphor screen,
24
a shadow mask,
25
a mask frame,
26
a magnetic shield,
27
a shadow mask suspension mechanism,
28
an electron gun,
29
, a deflection yoke, and
30
an external magnetic adjustment device.
As described above, the color cathode ray tube of this kind has a vacuum envelope compressing the panel portion
20
, the neck portion
21
, and the funnel portion
22
for connecting the panel portion
20
and the neck portion
21
.
The panel portion
20
is formed with the phosphor screen
23
coated with three-color phosphors in the inner surface, the electron gun
28
for emitting three electron beams in a line is housed in the neck portion
21
, and the shadow mask
24
having a multiplicity of apertures or a parallel array of narrow strips is arranged in the vicinity of the phosphor screen of the panel portion
20
.
The deflection yoke
29
is mounted exteriorly in the transition region between the funnel portion
22
and the neck portion
21
.
The electron gun
28
is housed in the neck portion
21
, and the stem
14
has a plurality of stem pins
13
annularly arrayed and sealed and extending therethrough to support electrodes of the electron gun and introduce various signal voltages from an external circuit.
Three electron beams (Bc, Bs×2) modulated by video signals and emitted from the electron gun are deflected in two directions, i.e. horizontally and vertically by horizontal and vertical deflection magnetic fields generated by the deflection yoke
29
, and are subjected to color selection at apertures in the shadow mask
24
to impinge on the respective phosphors thereby forming a color image.
FIG. 8
is a side view for explaining one example of an electron gun for a cathode ray tube. Reference numeral
1
designates a cathode,
2
a first grid electrode,
3
a second grid electrode,
4
a third grid electrode,
5
a fourth grid cathode,
6
a fifth grid electrode,
7
a sixth grid electrode,
7
a
a shield cup, and
8
glass rods for holding the electrodes in position (beading glass). Reference numeral
13
designates stem pins, and
14
a stem.
In
FIG. 8
, controlling and pre-focusing of electron beams are carried out by the first grid electrode
2
to the fourth grid electrode
5
. The fifth grid electrode
6
as a focus electrode and the sixth grid electrode
7
as an anode constitute a main lens.
The shield cup
7
a
is connected to the anode
7
(the sixth grid electrode) and serves as an electrode part for fixing contact springs for centering the electron gun in the neck portion and for supporting a getter.
These electrodes are mounted on the stem by being welded directly or through connecting leads, to the plurality of stem pins
13
which are annularly arrayed on the stem
14
, sealed thereto and extending therethrough, then the electrodes are inserted into the neck portion from its open end, and the periphery of the stem
14
is fused and fixed to the end of the neck.
FIG. 9
is an explanatory view of the operation for fusing and sealing the stem to the open end of the neck portion of the cathode ray tube. Reference numeral
10
designates an exhaust tubulation,
13
stem pins,
13
a
inner portions of the stem pins projecting into the interior of the neck portion,
14
a stem, and
21
a neck portion. An electron gun
28
is indicated by dotted lines.
As shown in
FIG. 9
, the stem
14
for supporting the electron gun
28
at its inner portions
13
a
projecting into the interior of the neck portion is formed of glass material, and is in the form of a flat disk whose outside diameter is smaller than that of the neck portion
21
.
Stem mounds
11
are formed at the bases of the inner portions of the stem pins by raising the glass material of the stem
14
to mechanically support the inner portions
13
a
of the stem pins and to prevent the loss of the vacuum.
After the electron gun
28
has been secured to the stem
14
, the electron gun is inserted from the open end of the neck portion
21
as indicated by the arrows, the outer peripheral portion of the stem is placed in contact with the open end of the neck portion, and the neck portion and the stem at their junctions are fused and sealed by heating them from outside the outer periphery thereof by a burner or the like.
After the stem is fused and sealed to the neck portion
21
and the vacuum envelope is evacuated to a desired vacuum with the exhaust tubulation
10
connected to a vacuum pumping system, the exhaust tubulation
10
is sealed off.
FIG. 10
is a sectional view of main parts for explaining a fused portion of the neck portion and the stem in sealing a conventional cathode ray tube. Reference numeral
12
designates a groove, and
15
a fused portion. The same reference numerals are used in
FIG. 10
as used for corresponding parts in
FIGS. 1
to
9
.
As explained in
FIG. 9
, in sealing the cathode ray tube, the stem
14
is placed in contact with the open end of the neck portion
21
, their junctions are heated and fused by using a burner or the like, the force is applied so that the stem
14
is somewhat pulled away from the neck portion
21
to thereby form a constricted portion in the fused portion
15
as shown in FIG.
10
.
In the aforementioned conventional cathode ray tube sealed off by fusing the stem
14
, a sufficiently large difference (R
1
−R
2
) between a distance (hereinafter also called an inner radius) R
1
from the tube axis to the inner wall in a region of the neck portion housing a major portion of the electron gun
28
supported on the inner portions
13
a
of the stem pins projecting into the interior of the neck portion, and a distance R
2
from the tube axis to the outside edge of the stem mounds
11
measured at half the axial height H of the stem mounds
11
, has been secured to thereby prevent the occurrence of crack in a fused portion of the stem.
Therefore, for example, a stem having a diameter of 15.24 mm of a circular array of stem mounds
11
(corresponding to a diameter of a stem pin circle) has been coupled to a neck portion having an outside diameter of 29.1 mm and an inside diameter of 23.9 mm. In this case, the minimum value of R
1
is approximately 12 mm and the maximum value of R
2
is approximately 9.3 mm, and the difference (R−R
2
) is nearly equal to 2.7 mm.
There has been a problem in that it is diffic
Koumura Hidehiro
Nakamura Takao
Nose Hisashi
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Patel Vip
LandOfFree
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