Funnel-and-neck sealing body for projection tube

Details Funnel-and-neck sealing body for projection tube Funnel-and-neck sealing body for projection tube

2002-08-28

2004-04-06

Patel, Ashok (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Envelope

C313S478000, C313S440000, C313S421000, C220S00210A

Reexamination Certificate

active

06717347

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a funnel-and-neck sealing body for projection tube.
2. Description of Related Art
As shown in
FIG. 6
, a glass member forming a cathode ray tube for a projection tube (projection tube, hereinafter) comprises a panel
30
whose inner surface is coated with fluorescent material, a neck tube
32
in which an electron gun is installed, and a funnel
33
connecting the panel
30
and the neck tube
32
. These elements arc sealed to each other with frit glass, or with fusing the elements themselves, thus a glass bulb
34
is formed.
The inside of the glass bulb
34
is highly vacuumed in order to make electrons emit out of the electron gun
31
, and a deflection yoke
35
is externally mounted between the neck tube
32
and the funnel
33
. Electron beams emitted from the electron gun
31
are controlled by the deflection yoke
35
to collide with the fluorescent material, thereby to make the fluorescent material emit light, in a fluorescent film coated on the inner surface of the panel
30
, and thereby the image is displayed.
The projection tube is different from the general consumer direct-view type cathode ray tube where the image displayed on the panel is directly viewed. For example, as shown in
FIG. 7
, the electron beams are made to collide with the fluorescent material on the inner surface of the panel
30
to emit light. The image displayed on the light-emitted surface is projected and enlarged by a lens set
37
onto a screen
39
that is separately arranged in front of the projection tube
38
. The viewer can observe, watch and view the enlarged projection image. Therefore, in comparison with the consumer cathode ray tube, the projection tube is required to have a higher light brightness. Increasing the light brightness can be achieved by increasing the strength and the amount that the electron beams emitted from the electron gun
31
collide with the fluorescent material on the inner surface of the panel
30
. However, in the projection tube
38
for enlarging and projecting the image, if the electron beams do not illuminate a very small area on the light-emitting surface of the projection tube
38
, the pixel of the enlarged and projected image becomes rough and the image quality might be reduced, so that the focus accuracy of the electron gun
31
has also to be increased. According to Ludwig Von Seidel's aberration theory, the spherical aberration, the comatic aberration and the astigmatism become better as the aperture of the lens, i.e., the diameter of the electronic lens of the electron gun
31
is larger.
According to the aforementioned reasons, in comparison with the consumer cathode ray tube of direct view type that has the same size, the electronic lens of the electron gun used in the projection tube has a larger aperture, so that the neck tube for installing the electron gun also has a larger outer diameter.
In recent years, with the requirements of high brightness, the high definition for projection tubes is further increased, and therefore, an electron gun having an electronic lens with a diameter larger than before has to be installed and the outer diameter of the neck tube has to be made larger accordingly. However, to enlarge the outer diameter of the neck tube will make the separation distance between the deflection yoke externally mounted on the neck tube and the electron beams passing through the inside of the neck tube become longer, which causes a reduction of the deflection sensitivity. In order to obtain a desired deflection sensitivity for the electron beams, an energy power larger than prior art has to be provided to the deflection yoke, or the deflection coil has to be increased in size to increase its output power. However, in the previous case, because of the power tolerance of the deflection yoke itself, the calorific quantity will increase and harmful effects due to the difference of the thermal expansion with the other parts might occur. For the latter case, because the length in the tube axis direction of the deflection coil becomes longer, the problem that the projection tube itself becomes larger is inevitable.
Additionally, for the projection tube that has to use a large electron gun, because the power consumption particularly required for activating the projection tube is large, to save power consumption is strongly demanded. The power consumption of the deflection yoke for deflecting the electron beams dominates among the total power consumption of the projection tube. Therefore, to particularly reduce the power for the horizontal deflection makes a significant contribution to saving the power consumption.
The power for the horizontal deflection is proportional to the inner diameter of the deflection coil and the acceleration voltage applied to the electron gun, and is inversely proportional to the length of the deflection coil. Therefore, in order to reduce the power for the horizontal deflection, to reduce the applied acceleration voltage, to reduce the frequency of the horizontal deflection, to reduce the inner diameter of the deflection coil, or to increase the length in the tube axis direction of the deflection coil has been considered. However, because to reduce the applied acceleration voltage will reduce the energy with which the electrons of the electron beams collide with the fluorescent material, the brightness of the fluorescent material will decrease. To reduce the frequency of the horizontal deflection will cause a reduction of the image quality. Furthermore, because a reduction of the inner diameter of the deflection coil will cause a reduction of the outer diameter of the neck tube, the diameter of the electronic lens of the electron gun installed in the neck tube has to be reduced, so that the focus accuracy required for the projection tube is reduced. To increase the length in the tube axis direction of the deflection coil will inevitably enlarge the projection tube.
SUMMARY OF THE INVENTION
According to the foregoing description, an object of this invention is to provide a funnel-and-neck sealing body for projection tube, which can contribute to make a projection tube installed a large electron gun therein compact, and to reduce the power consumption significantly, while maintaining the high brightness and the high definition required for projection tubes.
To achieve the foregoing objects, the invention provides the following funnel-and-neck sealing body for projection tube. The funnel-and-neck sealing body comprises a funnel having a substantially rectangular large opening to which a panel for projection tube is sealed, and a circular small opening; and a neck tube of substantially a cylindrical shape sealed to the small opening of the funnel. The neck tube has an electron gun installing region for installing an electron gun therein, and a yoke mounting region for mounting a deflection yoke externally thereon, wherein an outer diameter of the yoke mounting region is smaller than an outer diameter of the electron gun installing region.
In the above structure, preferably, a diagonal outer diameter of the large opening is 80 mm~330 mm, a ratio of the outer diameter of the electron gun installing region with respect to the diagonal outer diameter of the large opening is 9%~36%, and a ratio of the outer diameter of the yoke mounting region with respect to the outer diameter of the electron gun installing region is 50%~90%.
In addition, in the above structure, preferably, relationships of 2≦L/L
1
≦10 and 5≦L/L
2
are satisfied, where a length in a tube axis direction of the yoke mounting region is L
1
, a length in the tube axis direction of a connection region between the yoke mounting region and the electron gun installing region is L
2
, and a total length in the tube axis direction of the neck tube is L.
Additionally, the neck tube includes a flare type that contains an excess portion, which will be cut after the electron gun is inserted, at one end of the neck tube through which the electron gun is inserted,

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