Stem for cathode ray tube

Details Stem for cathode ray tube Stem for cathode ray tube

2001-07-24

2004-01-13

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Envelope

C313S4770HC, C313S482000

Reexamination Certificate

active

06677701

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application claims priority of application No. 2000-43279 filed in the Korean Industrial Property Office on Jul. 27, 2000, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a stem for a cathode ray tube, in which shapes of stem mounds are differentiated according to loads applied to inner leads so that cracks of the stem mounds and apertures blocking of a shadow mask due to the crack particles may be prevented.
(b) Description of the Related Art
In general, a cathode ray tube is a display for realizing a certain image by a phosphor screen with electron beams which are emitted from an electron gun, wherein a stem is mounted with a plurality of leads for fixing the electron gun in a bulb and connecting the electrodes of the electron gun to an external set circuit, so as to apply a predetermined voltage signal to the respective electrodes of the electron gun.
As shown in
FIG. 1
, a related art cathode ray tube includes a face panel
1
, a funnel
3
and a neck portion
5
which are integrally sealed and constitute a bulb
7
, wherein the face panel
1
is formed with a phosphor screen
9
on an inner surface and is mounted with a shadow mask
11
at a predetermined distance from the phosphor screen
9
, the funnel
3
has a deflection yoke
13
mounted on an outer peripheral surface, and the neck portion
5
has an electron gun
15
.
In the structure as above, as the electron gun
15
emits three electron beams to their corresponding red R, green G and blue B phosphor layers, the electron beams are deflected by magnetic fields which are generated by the deflection yoke
13
and form a raster on the phosphor screen
9
. The raster is divided into the corresponding R, G and B phosphor layers in the phosphor screen
9
by the shadow mask
11
serving as an color-selecting electrode, so that precise colors are displayed.
The electron gun
15
includes a cathode for emitting electrons, and a plurality of electrodes for forming an electronic lens by a potential difference and controlling focusing and acceleration degree of the electrons, wherein the cathode and the plurality of electrodes are connected to respective leads
19
which are attached to a stem
17
to be supplied with voltage signals from an external set circuit.
FIG. 2
is a front view of a related art stem and
FIG. 3
is a plane view of the stem.
Referring to FIG.
2
and
FIG. 3
, the stem
17
includes a stem part
21
in the shape of a circular disc to be integrally melted with an end of the neck portion
5
, an exhausting tube
23
mounted in the middle of the stem part
21
for connecting an inside of the bulb
7
to an unshown exhausting system, a plurality of leads
25
mounted along a periphery of the exhausting tube
23
and connected to the respective electrodes of the electron gun
15
, and a plurality of stem mounds
27
for fixing and supporting the respective leads
25
to the stem part
21
.
The leads
25
are divided into two parts, of which inner leads
25
a
are positioned inside the neck portion
5
with relation to the stem mounds
27
to be connected to the electron gun
15
and outer leads
25
b
are positioned outside the stem mounds
27
to be connected to the external set circuit.
According to the above structure, the inner leads
25
a
of the stem
17
are welded to the respective electrodes of the electron gun
15
directly or via an additional connection conductor, so that the stem
17
is integrated with the electron gun
15
. The neck portion
5
and the stem part
21
are heated and melted together by a well-known torch heating method under the state that the stem
21
is facing to an end of the neck portion
5
to facilitate insertion of the electron gun
15
into the neck portion
5
.
After fixing the stem
17
to the neck portion
5
, the exhausting system is driven to evacuate an inside of the bulb
7
by means of the exhausting tube
23
, and the inside of the bulb
7
is sealed in a high vacuum state after melting the exhausting tube
23
by the torch heating method, and cutting it.
As described above, the stem
17
is integrally joined to the neck portion
5
for serving to support the electron gun
15
in the bulb
7
, wherein the plurality of leads
25
and the stem mounds
27
which fix and support the leads
25
are formed to have a same diameter and shape, so that the plurality of inner leads
25
a
and the stem mounds
27
have the same load intensity characteristics.
The inner leads
25
a
are, however, applied with a bending deformation stress due to the load and welding of the electron gun
15
, since the whole melting and discharging procedure of the stem
17
and the neck portion
5
is carried out under the circumstances that the electron gun
15
is fixed in the stem
17
, and particularly, the load is not uniformly applied to all the inner leads
25
a
but is concentrated on some of the inner leads
25
a
which support the electron gun
15
.
Therefore, cracks are apt to be generated at the load-concentrated leads
25
a
due to the high load, so that the supporting force of the leads
25
becomes decreased due to the cracks, and beam passing apertures of the shadow mask
11
are blocked by glass powder which is generated in the stem mounds
27
and advances into the bulb
7
.
Such an apertures blocking of the shadow mask
11
disturbs passage of the electron beams and accordingly the phosphor screen
9
can not emit light, resulting in the formation of a black spot at a certain position.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a stem for a cathode ray tube in which stem mounds are reinforced to prevent cracks from being generated therein to accordingly prevent blockage of apertures of a shadow mask caused by glass powder from the cracks.
In order to achieve this object, the stem for a cathode ray tube includes a stem part of a circular disc type to be integrally sealed with an end of a neck portion, an exhausting tube mounted in the middle of the stem part for the exhausting of a bulb, a plurality of leads mounted to the stem part along a periphery of the exhausting tube and connected to respective electrodes of an electron gun for providing voltage signals, and a plurality of stem mounds mounted to the respective leads for fixing and supporting the leads on the stem parts and having different shapes depending on loads to be applied to the leads, wherein some of the stem mounds have an increased diameter as the loads applied to their corresponding leads increase.
In the stem for a cathode ray tube of the present invention, cracks of the stem mounds and the apertures blocking of the shadow mask due to the crack particles are effectively prevented.


REFERENCES:
patent: 4101803 (1978-07-01), Retsky et al.
patent: 4379978 (1983-04-01), Hockenbrock
patent: 6054805 (2000-04-01), Park et al.
patent: 6509682 (2003-01-01), Ishinagawa et al.

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