Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
2001-12-06
2004-04-20
Sember, Thomas M. (Department: 2875)
Electric lamp and discharge devices
Cathode ray tube
Envelope
C313S559000, C313S417000, C501S079000
Reexamination Certificate
active
06724139
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cathode ray tube, and in particular to a cathode ray tube having an indirectly heated cathode using a low-melting-temperature crystallized glass as an insulator for supporting a cathode sleeve.
In general, cathode ray tubes (CRTs), for example, color cathode ray tubes (CPTs) for use in color TV receivers and color cathode ray tubes (CDTs) for use in color display systems, have a phosphor screen formed on an inner surface of a faceplate of a panel portion of their vacuum envelope, a shadow mask having a large number of electron-beam transmissive apertures and disposed within the panel portion so as to face the phosphor screen, an in-line type electron gun housed within a neck portion of the vacuum envelope, and a deflection yoke mounted around the outside of a funnel portion of the vacuum envelope.
In operation of a color cathode ray tube, three electron beams emitted from the electron gun are deflected by the deflection yoke, and then impinge upon the pixels of corresponding colors of the phosphor screen, respectively, after passing through the electron-beam transmissive apertures in the shadow mask, thereby displaying a specified color image on the phosphor screen.
FIG. 4
is a schematic cross-sectional view of a color cathode ray tube for illustrating an example of its overall construction. In
FIG. 4
, reference numeral
41
denotes a panel portion,
42
is a phosphor screen,
43
is a neck portion for housing an in-line type electron gun
49
,
44
is a funnel portion for connecting the panel portion
41
and the neck portion
43
together, and
45
is a shadow mask, which is press-formed so as to be self-supporting and is welded at its periphery to a mask frame
46
. Reference numeral
47
denotes a magnetic shield,
48
is a mask suspension mechanism,
50
is a deflection yoke,
51
is an external magnetic correction device,
52
is an implosion proofing band,
53
are panel pins,
54
is a mask assembly, and
55
are stem pins.
In this color cathode ray tube, the panel portion
41
, the neck portion
43
and the funnel portion
44
form a vacuum envelope
56
, and three intensity-modulated electron beams (one center electron beam and two side electron beams) B are emitted from the electron gun
49
housed within the neck portion
43
, and then are deflected in a horizontal direction (the X direction) and a vertical direction (the Y direction) by horizontal and vertical deflection magnetic fields, respectively, generated by the deflection yoke
50
such that the three electron beams B scan the phosphor screen
42
two-dimensionally to reproduce an image. In
FIG. 4
, reference numeral
57
denotes an internal conductive coating which applies a high voltage introduced via an anode button
58
to a main lens of the electron gun
49
and a conductive film coated on the phosphor layer of the phosphor screen
42
.
The electron beams B are intensity-modulated by modulating signals such as video signals supplied by the stem pins
55
, then are controlled by electrodes such as an intermediate grid electrode supplied with a specified voltage, then are subjected to color selection by the shadow mask
45
disposed immediately in front of the phosphor screen
42
, and strike phosphor elements of the desired color (red, green or blue) constituting the phosphor screen
42
to thereby reproduce a specified image.
In the color cathode ray tubes of this kind, because of the cost of manufacture and ease of fabrication, the outer surface (also variously called the image-forming surface, the viewing surface and the face) of its panel portion is configured to have a large radius of curvature (or a large equivalent radius of curvature), that is, to be nearly flat, and on the other hand, the inner surface of the panel portion formed with the phosphor layer is configured to have a relatively smaller radius of curvature (or a relatively smaller equivalent radius of curvature) without impairing a sense of flatness of a picture displayed on the phosphor screen viewed from the outer surface side of the panel portion.
FIG. 5
is a side view of an essential part of the electron gun
49
provided with an internal voltage-dividing resistor and used in the color cathode ray tube shown in
FIG. 4
, as viewed in a direction perpendicular to a direction of the in-line arrangement of the three electron beams. The electron gun
49
for projecting the three electron beams in line is housed within the neck portion
43
of the vacuum envelope
56
of the color cathode ray tube.
The electron gun
49
includes an anode (the sixth grid electrode)
61
supplied with a highest voltage (an anode voltage), an intermediate grid electrode
62
supplied with a voltage divided from the anode voltage by the internal voltage-dividing resistor
72
, a cathode structure K for emitting the three electron beams, and a focus lens comprised of the grid electrode group
63
including plural electrodes, the fourth grid electrode
64
, the third grid electrode
65
, the second grid electrode
66
, and the first grid electrode
67
and focusing the electron beams emitted from the cathode structure K.
The electrodes
61
to
76
are fixed in the specified order with specified spacings therebetween by embedding portions of peripheries of the respective electrodes in a pair of insulating support rods
69
. A shield cup
68
is attached to the sixth grid electrode
61
, and springs (not shown) made of metal are welded at their respective ends to a sidewall of a front end of the shield cup
68
, and the other ends of the respective springs press resiliently against the internal conductive coating
57
made of material such as graphite and extending from the inner wall of the funnel portion
44
toward that of the neck portion
43
of the vacuum envelope
56
such that the anode voltage is supplied to the sixth grid electrode
61
via the anode button
58
sealed through the funnel portion
44
.
The internal voltage-dividing resistor
72
is attached to an outer surface of one of the pair of insulating support rods
69
facing the tube wall of the neck portion
43
. The internal voltage-dividing resistor
72
is provided with terminals
73
,
74
and
75
for electrical connections, the terminal
73
is connected to the sixth grid electrode
61
supplied with the anode voltage, the terminal
74
is connected to the intermediate grid electrode
62
, and the terminal
75
is connected to the earth.
A connecting tab
73
a
is attached to the terminal
73
, projects from it in a direction perpendicular to the central axis of the electron gun
49
, and is connected to the sixth grid electrode
61
. A connecting tab
74
a
projects from the terminal
74
, is connected to the intermediate grid electrode
62
, and thereby supplies a high voltage divided from the anode voltage by a factor corresponding to the ratio between the resistances in the internal voltage-dividing resistor
72
to the intermediate grid electrode
62
. A connecting tab
75
a
projects from the terminal
75
, is connected to one of the stem pins
55
via a connecting lead or the like, and is connected to a potential such as the ground potential (hereinafter the ground potential) via the one of the stem pins
55
outside the cathode ray tube.
A conductor
76
made of a metal wire has one end thereof connected to one electrode of the fifth grid electrode group
63
, surrounds the internal voltage-dividing resistor
72
and the insulating support rod
69
mounting the resistor
72
, and has the other end thereof connected to the one electrode of the fifth grid electrode group
63
on the side thereof opposite from the position at which the one end of the conductor
76
is connected, across the insulating support rod
69
. After the completed gun assembly is sealed into the neck portion
43
, the conductor
76
is heated by external high-frequency induction heating coil to evaporate a portion of metals contained in the conductor
76
and thereby to form a metal thin film on the inner tube wall of the neck portion
43
Antonelli Terry Stout & Kraus LLP
Macchiarolo Peter
Sember Thomas M.
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