Electric lamp and discharge devices – Cathode ray tube – Beam deflecting means
Reexamination Certificate
2003-01-21
2004-11-30
Williams, Joseph (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Beam deflecting means
C313S421000, C313S426000, C313S413000, C335S210000, C335S212000, C335S213000
Reexamination Certificate
active
06825603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cathode ray tube having a deflection yoke including a circular ferrite core and a deflection coil whose cross-section is in a rectangular shape for improving a deflection sensitivity of the cathode-ray tube, and more particularly to a cathode ray tube, in which one part of a vertical deflection coil having a rectangular shaped cross-section to improve a lead-in capability when winding the vertical deflection coil located between a ferrite core and the holder is separated by a predetermined gap from a holder that isolates a horizontal deflection coil and the vertical deflection coil
2. Background of the Related Art
FIG. 1
is a diagram illustrating a conventional cathode ray tube.
Referring to
FIG. 1
, the conventional cathode ray tube includes an electron gun
4
for emitting three electron beams, a fluorescent screen
1
on which a fluorescent substance is formed for colliding with the electron beams to generate lights, a shadow mask
2
for performing dichroic operations of the three electron beams, and a deflection yoke
3
for allowing the electron beams to be deflected at predetermined locations on the fluorescent screen
1
.
In particular, the deflection yoke
3
includes a horizontal deflection coil
31
for deflecting the electron beam emitted from the electron gun
4
installed in the cathode ray tube in the horizontal direction, a vertical deflection coil
33
for deflecting the electron beam in the vertical direction, a conic shaped ferrite core
34
for improving a magnetic efficiency by minimizing the loss of a magnetic force being generated from the horizontal deflection coil
31
and vertical deflection coil
33
, and a holder
32
for fixing the vertical deflection coil
33
, the horizontal deflection coil
31
and the ferrite core
34
at predetermined locations and isolating the horizontal deflection coil
31
and the vertical deflection coil
33
.
In addition, in a neck part of the deflection yoke
3
are formed a convergence yoke
35
for compensating a misconvergence due to an error of the manufacture process of the deflection yoke and the cathode ray tube, and a pair of ring-shape permanent magnets
36
.
FIG. 2
is a diagram illustrating an assembly process of the conventional cathode ray tube.
To give a brief description on the cathode ray tube with reference to
FIG. 2
, the horizontal deflection coil is installed in the inner part of the holder
32
, and the vertical deflection coil
33
is installed in the outer part of the holder
32
.
Then, the ferrite core
34
is provided in a manner to wind around the outer surface of the vertical deflection coil
33
.
The conventional deflection yoke
3
allows a current having at least 15.75 kHz frequency to flow to the horizontal deflection coil
31
and deflects the electron beam in the cathode ray tube in the horizontal direction using a magnetic field generated by the current.
Also, the deflection yoke
3
allows a current having a 60 Hz frequency to flow to the vertical deflection coil
33
and deflects the electron beam in the vertical direction using a magnetic field generated by the current.
A self-convergence type deflection yoke
3
for allowing three electron beams to compensate for a convergence on a screen without using separate additional circuit and additional device by using a nonuniform magnetic field generated by the horizontal deflection coil
30
and vertical deflection coil
33
, has been developing.
That is, by controlling a winding distribution of the horizontal deflection coil
31
and vertical deflection coil
33
and forming a barrel type or pin-cushion type magnetic field in respective regions (opening region, intermediate region and neck region), it is possible to have different deflection forces corresponding to locations of the three electron beams affect the electron beams, and therefore the electron beams converge on the same point though the respective electron beams have respective distances from beginning points to arrival points.
Also, in the case that a magnetic field is formed by flowing a current to the horizontal deflection coil
31
and the vertical deflection coil
33
, the magnetic field generated by the horizontal deflection coil
31
and the vertical deflection coil
33
is not strong enough to deflect the electron beams to the whole surface of the screen. Hence the ferrite core
34
having a high magnetic permeability is used to minimize a loss on a feedback path of the magnetic field, thereby improving an efficiency of the magnetic field and increasing a magnetic force.
FIG. 3
a
is a cross-sectional view of a conventional deflection yoke including a deflection coil, whose cross-section being in a rectangular shape, and a rectangular shaped ferrite core.
FIG. 3
b
shows a deflection coil having a rectangular shaped cross-section and a circular ferrite core.
Referring to
FIGS. 3
a
and
3
b
, when three electron beams pass through a magnetic field area, according to Fleming's left hand rule, a force applied to each of the three electron beams is deflected, being inversely proportional to the cube of the distance between the inner surface of the deflection coil and the electron beam. As shown in
FIG. 3
a
, because the deflection yoke including the deflection coil
33
and ferrite core
34
having the rectangular shapes respectively is closer to the electron beams than the deflection yoke having the circular deflection coil and the ferrite core, a deflection sensitivity can be improved.
Accordingly, in the case of the deflection yoke including the horizontal deflection coil and vertical deflection coil whose cross-sections are in rectangular shapes, the distance between the electron beam and the deflection coil is shorter by 20% than the conventional deflection yoke including the deflection coil whose cross-section is the circular shape. As a result, horizontal and vertical deflection sensitivities are greatly improved by 20-30%.
Also, given that the deflection coil
33
whose cross-section is the rectangular shape and the inexpensive circular ferrite core
34
as shown in
FIG. 3
b
are used, it is now possible to improve the deflection sensitivity and obtain enhanced cost reduction efficiency.
FIG. 4
shows a state how a conventional horizontal deflection coil whose cross section is a rectangular shape is wounded, and
FIG. 5
shows a state how a conventional vertical deflection coil whose cross-section is the rectangular shape is wounded.
Referring to
FIGS. 4 and 5
, the horizontal deflection coil
31
and the vertical deflection coil
33
are leaded-in and formed in a space between an upper former
20
and a lower former
21
. Because the horizontal deflection coil
31
, as shown in
FIG. 4
, is wound on the farther side of a former center line
40
, that is, beneath a diagonal line
41
, a distance which the horizontal deflection coil
31
must be leaded in from an entrance is short.
However, a relatively large number of vertical deflection coils
33
, as shown in
FIG. 5
, are located closer to the former center line
40
, that is, beneath the diagonal line
41
due to the deflection yoke property.
Accordingly, because the vertical deflection coil
33
must be leaded-in from the entrance toward the former center line
40
, the vertical deflection coil
33
is subjected to a great frictional force over the long distance in the course of winding.
Also, because the former surface of the vertical deflection coil
33
whose cross-section is the rectangular shape is bended almost perpendicularly in the vicinity of the diagonal line
41
, the frictional force becomes greater between the vertical deflection coil
33
and the former surface than a vertical deflection coil with a circular cross-section and the circular former surface.
Therefore, a problem arises in that the vertical deflection coil
33
whose cross-section is the rectangular shape has a poor lead-in capability upon winding.
FIG. 6
shows a cross-sectional diagram of a deflection yoke in a cathode ray tube
LG. Philips Displays Korea Co. Ltd.
Quarterman Kevin
Williams Joseph
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