Ferrite core in deflection yoke for Braun tube

Details Ferrite core in deflection yoke for Braun tube Ferrite core in deflection yoke for Braun tube

2000-11-17

2003-10-14

Kim, Robert H. (Department: 2882)

Electric lamp and discharge devices

Cathode ray tube

Beam deflecting means

C335S210000, C335S213000

Reexamination Certificate

active

06633116

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deflection yoke for a Braun tube, and more particularly, to a ferrite core in a RAC type deflection yoke employed for improving a deflection sensitivity of a Braun tube.
2. Background of the Related Art
In general, a color Braun tube is provided with an in-line type electron gun, in which a self-converging type deflection yoke with a non-uniform magnetic field is employed for converging three electron beams onto one dot on a fluorescent film as red(R), green(G), and blue(B) electron beams are emitted arranged on a horizontal line in parallel. Referring to FIGS.
1
~
2
B, a related art color cathode ray tube, and a RAC type deflection yoke applied thereto will be explained.
Referring to
FIG. 1
, the related art color cathode ray tube is provided with a panel
1
forming a front surface thereof, a fluorescent film
3
on an inside surface of the panel
1
having a coat of red(R), green(G), and blue(B) fluorescent materials applied thereon, a shadow mask
2
in rear of the fluorescent film
3
for selection of colors of the electron beams incident to the fluorescent film
3
, a funnel
6
welded to a rear of the panel
1
, an electron gun
5
fitted inside of a neck part in a rear portion of the funnel
6
for emission of electron beams
7
, and a RAC type deflection yoke
4
mounted to surround an outer circumference of the neck part in the rear portion of the funnel
6
for deflection of the electron beams emitted from the electron gun in a horizontal or vertical direction.
And, referring to
FIGS. 2A and 2B
, the RAC type deflection yoke
4
is provided with one pair of horizontal deflection coils
41
for deflecting the electron beams emitted from the electron gun
5
in the cathode ray tube in a horizontal direction, one pair of vertical deflection coils
42
for deflecting the electron beams in a vertical direction, a ferrite core
44
for reducing losses of magnetic forces generated by currents in the horizontal deflection coil
41
and the vertical deflection coil
42
to enhance a deflection efficiency, a holder
43
for fixing relative positions of the horizontal deflection coils
41
, the vertical deflection coils
42
, and the ferrite core
44
, physically holding and fastening the same, and insulating between the horizontal deflection coils
41
and the vertical deflection coils
42
and fastening the horizontal deflection coils
41
and the vertical deflection coils
42
to the cathode ray tube, a COMA free coil
45
mostly fitted to a neck side of the holder
43
for improving a coma aberration generated by a vertical barrel type magnetic field, a ring band
46
fitted to a neck side of the holder
43
for fastening the cathode ray tube and the deflection yokes
4
physically, and magnets
47
fitted to an opening side of the deflection yokes for correction of raster distortion of a picture.
In the meantime, referring to FIGS.
3
~
4
C, the rectangular ferrite core in the related art RAC type deflection yoke, and the vertical deflection coils fastened to the ferrite core will be explained in detail.
FIG. 3
illustrates a perspective view of the rectangular ferrite core in FIG.
2
A.
Referring to
FIG. 3
, the related art ferrite core
44
is provided with, when the related art ferrite core
44
is compared to the cathode ray tube, a small sized neck portion
44
c
identical to the neck part of the cathode ray tube, an opening portion
44
a
large sized compared to the neck portion
44
c
identical to a screen side of the cathode ray tube, and an intermediate portion
44
b
, an intermediate region of the neck portion
44
c
and the opening portion
44
a
. Particularly, the ferrite core has a section circular at the neck portion
44
c
, which gradually becomes non-circular as the section goes from the neck portion
44
c
to the opening portion
44
a
which is rectangular. That is, the intermediate portion
44
b
is a region of transition from a circle to a rectangle, and dashed lines in the intermediate portion
44
b
in
FIG. 3
indicate a point P where the transition from a circle to a rectangle starts.
FIG. 4A
illustrates a perspective view of the vertical deflection coils in
FIG. 2A
,
FIG. 4B
illustrates a front view of
FIG. 4A
, and
FIG. 4C
illustrates a side view of FIG.
4
A.
Referring to FIGS.
4
A~
4
C, the vertical deflection coils
42
are disposed on an inside of the rectangular ferrite core
44
and has a contour substantially similar to the foregoing ferrite core. That is, identical to the rectangular ferrite core
44
, the vertical deflection coils
42
also has a small sized neck portion
42
c
substantially similar to the neck part of the cathode ray tube, a large sized opening portion
42
a
substantially similar to a screen side form of the cathode ray tube, and an intermediate portion
42
b
which is an intermediate region of the neck portion
42
c
and the opening portion
42
a
. And, the vertical deflection coils
42
collectively have a section circular at the neck portion
42
c
, which gradually becomes non-circular as the section goes from the neck portion
42
c
to the opening portion
42
a
which is rectangular. That is, the vertical deflection coils
42
also have a point P of transition from a circle to a rectangle and the intermediate portion
42
b
, a region of transition from a circle to a rectangle starting from the point of transition.
In the meantime, the regions of transition from a circle to a rectangle of the rectangular ferrite core
44
and the vertical deflection coils
42
have a ratio of transition from a circle to a rectangle which becomes the greater as the region goes from the neck portion to the opening portion. The ratio of transition from a circle to a rectangle is defined as follows.
Referring to
FIG. 6
, a circle is drawn centered on a corner of a square which has a length HL in a horizontal direction axis ‘H’ and a length VL in a vertical direction axis ‘V’, taking a diagonal line as a radius ‘R’. And, )H is defined as a difference between the radius R and the horizontal side length of the square HL, and )V is defined as a difference between the radius R and the vertical side length of the square VL. And, a sum of )H and )V is defined as )HV, i.e., )HV=)H+)V, and the ratio of transition(transition ratio) from a circle to a rectangle is defined to be )HV/R. In a case of a true circle, when both )H and )V are “0”, the transition ratio is “0”, and in a case of a square, the transition ratio is approx. 0.6.
The operation of the aforementioned RAC type deflection yoke
4
will be explained.
In general, the horizontal deflection coils
41
have currents with a frequency equal to 15.75 KHz or over applied thereto, for deflecting the electron beams in the cathode ray tube in a horizontal direction by using a magnetic field formed as the currents are applied thereto. And, in general the vertical deflection coils
42
have currents with a 60 Hz frequency applied thereto, for deflecting the electron beams in a vertical direction by using a magnetic field formed as the currents are applied thereto. In the meantime, recently, self-convergence type deflection yokes are developed mostly, which permits convergence of the three electron beams on a screen by using a non-uniform magnetic field formed by the horizontal deflection coil
41
and the vertical deflection coil
42
, without using any additional circuits or devices, separately. That is, distributions of wounds of the horizontal deflection coils
41
and the vertical deflection coils
42
are adjusted, such that magnetic fields at respective portions(the opening portion, the intermediate portion, and the neck portion) are a barrel form or a pin-cushion form, for exerting different deflection forces to the three electron beams depending on positions of the three electron beams so as to converge the three electron beams which have different distances from starting points to arrival points onto the same point. Moreover, in the case of magnetic field formation by applyi

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