Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2000-02-07
2001-04-24
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
Reexamination Certificate
active
06222310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cathode-ray tube and, particularly, to an improvement of an electrode plate which constitutes an electron gun of a cathode-ray tube.
2. Prior Art
A cathode-ray tube (hereinafter referred to as a color cathode-ray tube) used for color image display is constituted by a panel unit which is an image screen, a neck unit which holds an electron gun, and a funnel unit which couples the panel unit to the neck unit. In the funnel unit is mounted a deflector which causes an electron beam emitted from the electron gun to scan a fluorescent screen applied to the inner surface of the panel.
The electron gun held in the neck unit is provided with various electrodes such as a cathode electrode, a control electrode, a focusing electrode and an acceleration electrode. The electron beam from the cathode electrode is modulated by a signal applied to, the control electrode, and is permitted to impinge on the fluorescent screen after having been imparted with a required sectional shape and energy through the focusing electrode and the acceleration electrode. In the course of arriving at the fluorescent screen from the electron gun, the electron beam is deflected in a horizontal direction and in a vertical direction by the deflector provided in the funnel unit so as to form an image on the fluorescent screen (Japanese Patent Laid Open No. 215640/1984).
FIG. 16A
is a plan view of an electrode (G
3
electrode) which constitutes the electron gun provided in a conventional cathode-ray tube, and
FIG. 16B
is a sectional view of the G
3
electrode along the line B—B′ of FIG.
16
A. In these drawings, symbol G
3
denotes a G
3
electrode, E
1
denotes a first electrode plate which constitutes the G
3
electrode G
3
, symbol E
2
denotes a second electrode plate which constitutes the G
3
electrode G
3
, symbols H denote beam passage holes. Each of the first and second electrode plates E
1
, E
2
has three in-line beam passage holes H. Symbols S denotes bead supports (supports of bead glass not shown) provided to the first electrode plate E
1
.
A conventional G
3
electrode G
3
has been formed by welding two electrode plates together, i.e., by welding together a first electrode plate E
1
having bead supports S and a second electrode plate E
2
having three beam passage holes H. Therefore, the thickness of the first electrode plate E
1
where bead supports S are formed is different from that of the second electrode plate E
2
where the beam passage holes H are bored, developing steps in the boundary between the two. The reason why the plates with different thicknesses are used and a step is formed is to decrease the gap between the G
2
electrode (not shown) and the G
3
electrode G
3
in order to improve the focusing performance without deteriorating the breakdown voltage characteristics.
Conventionally, as shown in
FIGS. 16A and 16B
, since two electrode plates E
1
and E
2
are welded together, the productivity is low and the manufacturing cost is high. Furthermore, when a piece of electrode plate is subjected to coining by press-machining in order to obtain an electrode having a step, there arises a problem that the tools are often damaged due to the lack of sufficient strength.
SUMMARY OF THE INVENTION
The object of the present invention is to produce a one piece electrode plate with a step where a portion having beam passage holes and a portion having bead supports are formed in one body, maintaining a good productivity without increasing the cost of manufacturing, and preventing the machining tool from being damaged, by solving the aforementioned problems.
The above-mentioned object of the present invention is accomplished by a cathode-ray tube which has ann electron gun that includes a one piece electrode plate, wherein the electrode plate has a plurality of beam passage holes and bead supports, a portion having the beam passage holes and a portion having the bead supports are formed as a unitary or one piece structure, the two portions have different thicknesses, and steps are obliquely formed along the boundaries between the two portions.
Furthermore, a cathode-ray tube of the present invention has an electron gun that includes an electrode plate made by fabricating a metal plate such that a portion provided with a plurality of beam passage holes and a portion provided with bead supports are integrally formed in one piece, the two portions having different plate thicknesses, and accordingly steps are formed along the boundaries between the two portions, by punching the metal plate into a predetermined shape by press-forming, and then further punching the metal plate to make the beam passage holes.
According to the present invention, welding is eliminated since the portion having beam passage holes and the portion with bead supports are integrally formed together in one piece which have different thicknesses. Therefore, the productivity is improved and the manufacturing cost decreases. Moreover, since use is made of a one piece metal plate that has a step in advance, no coining is required or the forming rate of coining is small, making it possible to prevent the machining tools from being damaged during the press-forming. Besides, since the step is obliquely formed, the burden of the punching tools can be small and is prevented from being damaged.
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patent: 5146133 (1992-09-01), Shirai et al.
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patent: 5241246 (1993-08-01), Lapatovich et al.
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Endo Satoru
Mera Takeshi
Sugiyama Mitsuhiro
Antonelli Terry Stout & Kraus LLP
Day Michael H.
Hitachi , Ltd.
Santiago Mariceli
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