Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2000-08-31
2003-02-18
Chen, Sophia S. (Department: 2852)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S257000, C313S451000
Reexamination Certificate
active
06522059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode ray tube (CRT), and more particularly, to an electron gun mounted in a neck portion of a CRT, for exciting a phosphor layer.
2. Description of the Related Art
In general, CRTs are employed in projectors, oscilloscopes, monitors, TV receivers and the like, and an example of a CRT is shown in FIG.
1
.
As shown, the CRT includes a bulb
10
having a screen
12
with a phosphor layer
11
, and an electron gun
20
sealed in a neck portion
13
of the bulb
10
. A deflection yoke
15
for deflecting an electron beam emitted from the electron gun
20
is installed in a cone portion
14
of the bulb
10
. Here, the bulb
10
may be formed by sealing a panel and a funnel together. Also, a shadow mask frame assembly may be mounted inside the panel.
There are a variety of electron guns that are sealed into the neck portion according to the type of CRT, that is, either a monochrome CRT or a color CRT, the alignment of electrodes, and the states of voltages applied to various electrodes. One exemplary CRT, as disclosed in U.S. Pat. No. 4,904,898, is illustrated in FIG.
2
.
As shown, an electron gun
20
includes a cathode
21
for emitting thermal electrons, a control electrode
22
, a screen electrode
23
, upper and lower focusing electrodes
24
and
25
separately installed adjacent to the screen electrode
23
, and a final accelerating electrode
26
surrounding the end of the upper focusing electrode
25
. The cathode
21
and the respective electrodes
22
-
26
constituting the electron gun
20
are supported by a pair of bead glasses
27
at a predetermined gap.
The electrodes
22
-
26
are assembled by the bead glasses
27
as follows. First, a spacer is inserted between adjacent electrodes using an assembling set (not shown) to support the electrodes
22
-
26
in a state in which an electronic lens is formed by application of a voltage. In this state, the bead glasses
27
are heated to a half-melted state. When the heating of the bead glasses
27
is completed in the above-described manner, the heated bead glasses
27
are pressed at either side of the electron gun
20
so that buried portions
28
of the respective electrodes
22
-
26
are embedded in the bead glasses
27
and cooled.
However, the above-described assembling method in which the respective electrodes
22
-
26
are fixed to the bead glasses
27
, has several problems in that off-axis electrode alignment may occur and a distance variation between electrodes may be increased due to fabrication tolerance of a spacer used for maintaining a constant gap between adjacent electrodes or deformation occurring when the heated bead glasses
27
are cooled.
In particular, the cathode
21
, the control electrode
22
and the screen electrode
23
, forming a triode of the electron gun
20
, sensitively affect the characteristics of the electron gun. Due to the above-stated distance variation or off-axis electrode alignment, enhanced focusing characteristics of the electron gun cannot be attained. Thus, conventionally, in order to detect inferior of electron gun products, the alignment of all electron guns has been examined. However, since the conventional examination method requires many operational processes, it is not possible to enhance productivity.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an electron gun for a cathode ray tube, which can improve focusing characteristics by solving distance variation between a cathode and electrodes forming a triode of the electron gun and enhancing the alignment of electrodes.
It is another object of the present invention to provide an electron gun for a cathode ray tube, which can reduce electrode deformation due to a pressing force of bead glasses when electrodes forming a triode are fixed to the bead glasses.
To accomplish the first object of the present invention, there is provided an electron gun for a cathode ray tube including a cathode assembly, a control electrode and a screen electrode installed adjacently to the cathode assembly, and combined so as to be spaced a predetermined gap apart from each other by a gap maintaining means, a plurality of focusing electrodes sequentially installed from the screen electrode, to form an auxiliary lens and a main lens, and bead glasses into which buried portions of the cathode assembly and the respective electrodes are embedded to be supported.
In the present invention, the gap maintaining means which maintains the gap between the two electrodes, may be formed by adhering a ceramic member to the electrodes. In the case where the screen electrode and the control electrode are combined, the buried portions may be installed only at one side of either the control electrode or the screen electrode.
REFERENCES:
patent: 4414485 (1983-11-01), Marschka
patent: 4631443 (1986-12-01), Sigmund
patent: 4904898 (1990-02-01), Penird et al.
patent: 5028838 (1991-07-01), Askew et al.
patent: 5892322 (1999-04-01), Muchi et al.
patent: 05-325816 (1993-12-01), None
patent: 06-187920 (1994-07-01), None
patent: 10-064445 (1998-03-01), None
Jung Bong-wook
Kim Sang-kyun
Kim Sang-mook
Park Duk-sung
Chen Sophia S.
Samsung SDI & Co., Ltd.
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