Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
1999-12-02
2003-10-21
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S402000, C313S403000
Reexamination Certificate
active
06635980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color selection mechanism for a color cathode-ray tube used in, for example, color television receivers, display apparatuses and so on.
2. Description of the Related Art
As a color selection mechanism for a color cathode-ray tube, an aperture grille (a color selection called an aperture grille)
30
as shown in
FIG. 1
is known.
As for this color selection mechanism
30
, there is provided a frame-shaped metal frame
32
which is formed of a pair of opposed support members
37
U and
37
D and elasticity applying or providing members
38
R and
38
L extended across the support member
37
U to
37
D. Between the opposed support members
37
U and
37
D of this frame
32
, there is extended a so-called color selection electrode thin plate
31
having an arrangement including a large number of grid elements
33
and slit-shaped electron beam transmitting holes
35
formed between adjacent grid elements
33
.
The support members
37
forming the frame
32
serve as beams for holding the thin plate. The elasticity providing members
38
have a property a spring, and serve as a bow for absorbing plastic deformation caused in the fabrication process of the cathode-ray tube and temporary extension caused by beam irradiation during the operation of the cathode-ray tube. The thin plate needs to have a predetermined tension so as not to cause shaking in the grid elements even for voices from a loudspeaker and an external vibration and shock.
When welding the thin plate to the frame
32
, therefore, tension is applied to the thin plate in the extension direction “g” shown in
FIG. 1
, and compressive force (so-called turnbuckle) is applied to the support members
37
U and
37
D of the frame
32
conversely in such a direction “h” as to pressurize and compress the space between the support members
37
U and
37
D.
After such welding is conducted, when the pressurization is removed, the compressive force of the frame
32
is released and the thin plate is fixed to the frame
32
in such a state that tension is always generated in the thin plate. If this tension is low, then the grid elements
33
are vibrated by an external shock, a vibration of the loudspeaker or the like, and consequently the impinging positions of the electron beam thereon are not fixed, resulting in color shifts and disturbed images.
Especially in such a frame that joint points of the support members
37
and the elasticity providing members
38
are selected at the ends of the support members
37
, deflection at the central part of the support members
37
becomes large and hence a predetermined tension cannot be ensured, resulting in a problem.
As shown in
FIG. 2A
, the frame
32
of the color selection mechanism
30
has an L-shaped section. The frame
32
has such a shape that a longitudinal length “h” and a lateral length “d” of the L shape are the same in both its central part and end parts. The position and thickness of the frame
32
are determined so as to minimize an interference margin distance “m” between an end part
37
d
of the support
37
and an electron beam E.
For pressurizing the frame
32
and obtaining a predetermined tension distribution over the whole surface of the thin plate, the support members
37
must be tough, and increased weight of the frame
32
poses a problem. Therefore, attempts to increase the mechanical strength (geometrical moment of inertia) has been made. For example, the plate thickness of the support members
37
is increased while maintaining margin distance “mc” and “me” for the electron beam E. Furthermore, the dimension of the L shape as a whole is increased by suitably selecting the horizontal/lateral ratio h/d of the dimension of the L shape as shown in
FIG. 2B
(although the horizontal/lateral ratio h/d is constant in the range from the end parts to the central part), or the like.
Since the conventional support members
37
are shaped so that the end parts and the central part will have the same sectional shape (i.e., the same longitudinal/lateral ratio of the dimension of the L shape), however, the mechanical strength is determined on only the plate thickness from the problem of the electron beam cut, and consequently the degree of freedom of the design is low.
Especially, in a frame for a large sized tube, the weight becomes extremely large. The increased frame weight not only increases the cost but also aggravates the shock resistance of the cathode-ray tube. In addition, it is necessary to prepare various kinds of plate thickness of the frame material according to predetermined strength values of model units, and hence it is difficult to decrease the stock of materials.
Furthermore, in the above described improvement method, fabrication is difficult and the cost increases significantly. For its application to a general purpose cathode-ray tube; therefore, there are many problems.
SUMMARY OF THE INVENTION
In view of the above described points, an object of the present invention is to provide a cathode-ray tube and its color selection mechanism having an excellent quality and improved in mechanical strength without being increased in weight by improving the shape of the support members.
According to a color selection mechanism of the cathode-ray tube of the present invention, a geometrical moment of inertia representing the mechanical strength of a frame can be freely set by changing a ratio of a longitudinal dimension to a lateral dimension of an L-shaped section of each support member stepwise from a central part of each support member to each of end parts thereof without changing the whole width of the L-shaped section.
According to the color selection mechanism of the present invention, it becomes possible to increase the mechanical strength of the frame by using a single material without increasing the weight of the support member. In particular, it becomes possible to improve the shock resistance of a large-sized cathode-ray tube. And it becomes possible to reduce the manufacturing cost thereof.
According to a cathode-ray tube of the present invention, there is provided a color selection mechanism in which a ratio of a longitudinal dimension to a lateral dimension of an L-shaped section of each of a pair of support members is changed stepwise from a central part of each of the pair of support members to end parts thereof. As a result, it becomes possible to increase the mechanical strength of the central part of the support members without increasing the weight of the frame itself. Since the tension of the central part of the color selection electrode thin plate can be increased, the shock resistance of the cathode-ray tube can be prevented from being aggravated by an increase of the frame weight.
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patent: 4291253 (1981-09-01), Ohkoshi et al.
patent: 4495437 (1985-01-01), Kume et al.
patent: 4547695 (1985-10-01), Rath
patent: 5550428 (1996-08-01), Kume et al.
patent: 5554909 (1996-09-01), Brennesholtz
patent: 5576595 (1996-11-01), Inoue
patent: 5742116 (1998-04-01), Maki et al.
patent: 5751098 (1998-05-01), Ito et al.
patent: 08124493 (1996-05-01), None
Sanford I. Heisler, PE, Wiley Engineer's Desk Reference, 1998, John Wiley and Sons, Inc., 2ndedition, pp. 84,85 and 92.
Kananen Ronald P.
Patel Ashok
Rader & Fishman & Grauer, PLLC
Sony Corporation
Zimmerman Glenn
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