Electric lamp and discharge devices – Cathode ray tube – Beam deflecting means
Reexamination Certificate
1998-12-14
2001-07-31
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Beam deflecting means
C335S210000, C335S212000, C313S412000
Reexamination Certificate
active
06268689
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an in-line type color cathode ray tube (CRT), and more particularly, to a convergence magnet assembly installed in the neck of a CRT for adjusting the static convergence of an electron beam of the CRT.
2. Description of the Related Art
Generally, in a color CRT having in-line type electron guns, the axes of three electron guns are arranged in the same plane including the tubular axis of the CRT such that the paths of two outside electron beams emanating from the electron guns located on both sides of the central electron gun will be symmetrical with respect to the path of the electron beam emanating from the central electron gun. Thus, it is advantageous to construct the electron gun assembly of such a CRT to cause the electron beams emanating from the respective guns but not deflected by deflecting means to converge at the center of a fluorescent screen located in front to the electron gun assembly so as to produce clean pictures.
However, it is difficult to cause picture tubes to satisfy such ideal conditions due to manufacturing errors in components parts of the tube or permissible dimensional allowances of the component parts.
For this reason, the color CRTs generally have slight variations in the path characteristics of the electron beams. It is known that the paths of electron beams are modified to compensate for such variations in electron beam path characteristics. The paths of the electron beams can be modified by an adjustable magnetic field, which has been used to provide a required color purity adjustment as well as static convergence adjustment.
That is, as shown in
FIG. 1
, the color purity has been adjusted by relatively rotating two annular shaped two-pole permanent magnets
11
and
11
′ mounted parallel to each other on a neck portion
101
of a CRT
100
, surrounding the paths of the electron beams. Also, a static convergence adjustment has been accomplished by providing two annular shaped four-pole permanent magnets
12
and
12
′ and two annular shaped six-pole permanent magnets
13
and
13
′ mounted parallel to each other on the neck portion
101
of the CRT surrounding the paths of the electron beams. When the magnet assembly
10
is aligned, the intensity of the magnetic field of the magnet assembly is maximized. On the other hand, when two permanent magnets are rotated relative to each other over a predetermined angle, e.g., 180°, 90° or 60°, the intensity of the magnetic field of the magnet assembly is minimized.
Where the CRT is ideally manufactured according to a design rule, a static convergence error is not generated or few errors are generated. Thus, it is not necessary to provide the magnet assembly. The static convergence is dislocated due to the minimum magnetic field of the magnet assembly mounted on the neck portion of the CRT. Accordingly, the convergence magnet assembly should be manufactured such that shifting of an electron beam is minimized. In the magnet assembly having a minimum beam shift, as shown in
FIG. 2
, if the distance OCV between the outer two electron beams, among three electron beams in an in-line arrangement, and the distance CCV from the midpoint of the distance OCV and the central beam deviate from the range A of the minimum shift amount, it is difficult to adjust static convergence.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a convergence magnet assembly for a cathode ray tube (CRT), which can converge the minimum adjustable amount to zero, by extending the range of adjustment of static convergence of an electron beam.
It is another objective of the present invention to provide a convergence magnet assembly for a CRT, which can improve picture resolution by improving characteristics corresponding to adjustment of purity and convergence.
To achieve the first objective, there is provided a convergence magnet assembly for a cathode ray tube (CRT) comprising:
at least one pair of magnet rings having magnetized portions at predetermined angular intervals and installed at a neck portion of the CRT, for static-convergence of three electron beams in an in-line arrangement; and
correction means having a correction ring magnetized by an odd number of at least three poles on at least one side adjacent to electron beams at either side among three electron beams to intentionally increase the electron beam shift amount by the pair of magnet rings.
According to another aspect of the present invention, there is provided a convergence magnet assembly according to claim
6
, wherein the intensity of the magnetic field caused by the central pole among three poles magnetized on the correction ring is stronger than that caused by the pole disposed at either side thereof.
REFERENCES:
patent: 3808570 (1974-04-01), Thompson et al.
patent: 4091347 (1978-05-01), Barbin
patent: 4310819 (1982-01-01), Morita et al.
patent: 4670726 (1987-06-01), Ogata et al.
patent: 5227753 (1993-07-01), Hirai et al.
patent: 5289149 (1994-02-01), Nishita et al.
patent: 5708323 (1998-01-01), Okamoto
patent: 5757122 (1998-05-01), Kim
patent: 5955830 (1999-09-01), Uyama
Gerike Matthew J.
Leydig , Voit & Mayer, Ltd.
Patel Ashok
Samsung SDI & Co., Ltd.
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