Cathode ray tube

Details Cathode ray tube Cathode ray tube

2001-04-13

2002-03-05

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Plural beam generating or control

C313S447000, C315S381000, C315S382000

Reexamination Certificate

active

06353281

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to color cathode ray tubes and, more particularly, to a color cathode ray tube with an in-line type electron gun assembly for emission of a plurality of parallel electron beams extending in one plane.
Color cathode ray tubes, such as television picture tubes and display tubes, are widely employed as visual monitoring devices for use in receiving and displaying over-the-air broadcast TV programs or for use with a variety of types of information processing apparatus or equipment.
Color cathode ray tubes of this type are typically designed to include an evacuated outer envelope structure, which is structured from a panel portion having a fluorescent or phosphor screen formed on its inner surface, a neck portion accommodating therein an electron gun assembly for emission of more than one electron beam, and a cone-shaped portion, also known as a funnel section, for connecting the panel and the neck portion together. And, the electron gun assembly is typically designed to include in-line guns for giving off a plurality of parallel electron beams extending in one plane, i.e. the in-line plane.
FIG. 10
is a side view of an in-line electron gun assembly of the type used in prior art color cathode ray tubes, as seen from the in-line layout direction of electron beams. In
FIG. 10
, reference numeral “
20
” designates a cathode;
21
denotes a first grid electrode functioning as a control electrode; and,
22
indicates a second grid electrode acting as an acceleration electrode. The cathode
20
, first grid electrode
21
and second grid electrode
22
constitute an electron beam generator unit (triode unit). Numeral
23
denotes a third grid electrode;
24
indicates a fourth grid electrode;
25
denotes a fifth grid electrode;
26
denotes sixth grid electrode;
27
denotes an anode;
28
denotes a shield cup; and
29
denotes a dielectric support structure (multi-foam glass).
Three electron beams as generated by the triode unit consisting of the cathode
20
and first grid electrode
21
and second grid electrode
22
are accelerated and pre-focused by an electron lens system, formed of the third grid electrode
23
and fourth grid electrode
24
, as well as the fifth grid electrode
25
. Then, the electron beams are focused by a main electron lens, formed of the sixth grid electrode
26
and anode
27
, to direct the beams toward the phosphor screen. With the electron gun assembly of this type, the first grid electrode
21
and second grid electrode
22
and fourth grid electrode
24
are each comprised of a plate-shaped electrode, whereas those electrodes (fifth grid electrode
25
, sixth grid electrode
26
, and anode
27
) making up the focusing electron lens and main electron lens are constituted from cup-shaped electrodes.
The third grid electrode
23
has an electron beam passage opening or hole on the side thereof facing the second grid electrode
22
, which is less in aperture diameter than an electron beam passage hole on the side thereof facing the fourth grid electrode
24
.
FIGS. 11A and 11B
are a front view and a partially broken sectional view, respectively, of the third grid electrode
23
of FIG.
10
.
FIG. 11A
is a front view of the third grid electrode as viewed from the side facing the second grid electrode, whereas
FIG. 11B
is a partly broken sectional view from the side.
The third grid electrode
23
consists essentially of two separate electrode components. A first component
231
constituting the third grid electrode is a cup-shaped electrode component having electron beam passage holes
233
of small aperture or bore diameter. A second electrode component
232
making up the third grid electrode
23
is a plate-shaped electrode component having electron beam passage holes
234
greater in bore diameter than the electron beam passage holes
233
. The third grid electrode is such that the first component
231
and second component
232
are bonded and soldered together to provide an integral or solid structure. Note that numeral
235
designates tabs to be embedded in the multi-foam glass for supporting the grid electrode.
FIG. 12
depicts a sectional view of the electrode structure as seen along line XII—XII in FIG.
11
A. The first component
231
is a cup-shaped component that has three electron beam passage holes
233
on the side facing the second grid electrode
22
. The second component
232
is a plate-shaped component having three electron beam passage holes
234
greater in bore diameter than the electron beam passage holes
233
. These two components are bonded and soldered together to thereby provide a third grid electrode
23
of solid structure. The aperture or bore diameter Db of the electron beam passage holes
233
on the second grid electrode side as formed in the first component
231
is less than the bore diameter Dt of the electron beam passage holes
234
on the fourth grid electrode side as formed in the second grid electrode
232
(Dd>Dt).
The third grid electrode
23
is thus arranged to employ two components that are soldered together with the center axes of electron beam passage holes of both components being identical to each other. However, the accurate positional alignment between the center axes of the electron beam passage holes of the two separate electrode components remains difficult, which in turn makes it difficult to assemble the third grid electrode with high accuracy. In addition, as respective components (the first component and second component) exhibit their own deviation in the manufacture thereof, the resulting third grid electrode
23
as manufactured by assembly of these components exhibits an even greater deviation. Furthermore, the third grid electrode is located adjacent to the triode unit. Due to such arrangement, minute deformation of the third grid electrode can significantly affect the electron beams that are being emitted.
The first component of the prior art third grid electrode shown in
FIG. 12
is designed to have a rise-up portion
240
, which is positioned outside of the one side electron beam passage hole in the in-line direction. In other words, the rise-up portion
240
is in close proximity to the side electron beam and yet far from the central electron beam. As a result, the electric field acting on the side electron beam will be different in shape from the electric field acting on the central electron beam. Such a difference between the electric field for the side electron beam and the electric field for the central electron beam in turn causes the central electron beam and the side electron beam to differ from each other in sectional shape also.
FIG. 13
is a process flow diagram for explanation of a manufacturing method of the prior art third grid electrode, which is formed of two components. The first component is formed by press-machining techniques into convex shape; then, three electron beam passage holes are formed in the top surface of the convex component. Barrel processing is then applied to the resultant structure to remove away burrs residing at the electron beam passage holes. The second component is manufactured by a method including the steps of applying press-machining to a plate body to form three electron beam passage holes, and then removing burrs at these electron beam passage holes through barrel processes.
Then, the first component and the second component are bonded with the centers of respective electron beam passage holes in alignment with each other, and the components are then soldered together into an integral or solid structure.
FIG. 14
is a side view of another example of a conventional in-line electron gun module, wherein those parts identified with the same reference numerals correspond to the same functional portions in FIG.
10
. With an electron gun unit of this type, the first grid electrode
21
and second grid electrode
22
, as well as the third grid electrode
23
, are structured from plate-shaped electrodes, whereas those electrodes constituting the focus electron lens and main

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