Funnel for cathode ray tube

Details Funnel for cathode ray tube Funnel for cathode ray tube

2002-04-17

2003-11-25

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Envelope

C313S481000, C313S553000, C417S048000

Reexamination Certificate

active

06653774

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a funnel used for a cathode ray tube, and specifically relates to a funnel for a cathode ray tube, on an inner wall of a side wall portion of which an anode button is sealed for mounting a getter mounting body and protrusions are formed for restricting a turn of the getter mounting body around the anode button.
As is well known, a cathode ray tube includes a panel on which an image is projected, a funnel, and a neck tube in a tube shape with a small diameter as principal glass parts. As shown in
FIG. 5
, a funnel
1
is provided with a side wall portion
4
which is gradually decreasing in diameter in a direction from a seal edge surface
2
provided for sealing the panel toward a neck tube
3
. An anode button
6
is sealed and embedded at a predetermined position on an inner wall
5
of the side wall portion
4
. Frit glass is used for fusing to join the seal edge surface
2
of the funnel
1
to a seal edge surface of the panel in a manufacturing process for the cathode ray tube, and this process seals the panel to the funnel
1
.
The funnel
1
is molded such that high temperature molten glass gob is supplied to a mold comprising a bottom mold and a shell mold, in this state, a plunger is pressed against the gob to apply a pressing force, thereby, the molten glass gob moves up to a part corresponding to the side wall portion
4
in a direction toward the seal edge surface
2
while the molten glass gob is pressed and extended.
On the other hand, in the manufacturing process for the cathode ray tube after molding the funnel
1
, the inside of the cathode ray tube is evacuated after the funnel
1
is sealed to the panel, a high frequency irradiation from the outside of the cathode ray tube heats and vaporizes getter
7
such as barium held on the inner wall
5
of the funnel
1
, the getter
7
reacts with a small amount of residual air remaining inside the cathode ray tube, and thereby the vacuum increases to about 10
−6
Pa.
As means for holding the getter
7
on the inner wall
5
of the funnel
1
in a preceding process, the getter
7
is mounted to one end of an elastic metal piece
8
, which serves as a mounting member, to form a getter mounting body
10
, the elastic metal piece
8
is attached to the anode button
6
sealed and embedded on the inner wall
5
of the side wall portion
4
, and an elastic force of the elastic metal piece
8
presses the getter
7
against the inner wall
5
of the side wall portion
4
. When the elastic metal piece
8
is attached to the anode button
6
, a protruding terminal in a spherical or cylindrical shape formed on the anode button
6
is engaged with an engaging hole
8
a
formed through the elastic metal piece
8
.
The elastic force of the elastic metal piece
8
to which the getter
7
is attached simply allows the anode button
6
to support the elastic metal piece
8
. When a mechanical vibration acts during transporting or handling the cathode ray tube, the elastic metal piece
8
turns around the anode button
6
, and the position of the getter
7
is displaced from a desired initial position.
As a result, when the high frequency heating is performed on the getter
7
from the outside of the cathode ray tube after the panel is sealed to the funnel
1
, because the target is so displaced that the heating and vaporizing of the getter is obstructed, an inner atmosphere in the cathode ray tube does not reach required high vacuum, and defective emission of the electron beam, and consequently, a degraded picture receiving characteristic are generated. In this case, because the inside of the cathode ray tube is evacuated, it is extremely difficult to adjust the getter position, and consequently it becomes impossible to apply the cathode ray tube to a practical use.
To solve this problem, Japanese Utility Model Laid-Open Publication No. Hei. 3-8855 discloses a technology wherein a pair of protrusions made of glass-buildups are formed on the inner wall
5
of the funnel
1
. Namely, a pair of the protrusions
9
are formed in a neighborhood of the anode button
6
on the inner wall
5
so as to clamp the elastic metal piece
8
from the both sides, and the existence of the pair of protrusions
9
prevents the getter mounting body
10
from turning around the anode button
6
.
However, prior art including the disclosed technology in the publication gives no consideration to the shape of the protrusions
9
, and the protrusions
9
are simply formed just for preventing the turn of the getter mounting body
10
. Specifically, as shown in
FIG. 6
, the conventional protrusions
9
are formed such that the most protruded part
9
a
on the basis of the inner wall
5
of the funnel
1
continues to the inner wall
5
at a side of the seal edge surface
2
through a first slope
9
b
, and the most protruded parts
9
a
continues to the inner wall
5
at a side of the neck
3
through a second slope
9
c
. The first slope
9
b
and the second slope
9
c
are set to the same inclination, namely the same slope angle, on the basis of the inner wall
5
.
In this case, there is a large difference in flow speed between the molten glass flowing on parts corresponding to the protrusions
9
and the molten glass flowing on parts corresponding to the inner wall
5
in the neighborhoods of the protrusions
9
, which are not protruded, when the molten glass moves up on the part corresponding to the side wall portion
4
toward the seal edge surface
2
. When the two flows of the molten glass are different from each other in the flow speed and they merge together in the neighborhoods of the end parts at the side of the seal edge surface
2
corresponding to the protrusions
9
, the flow of the molten glass is disturbed and obstructed in the neighborhoods of the end parts. As a result, in the molded funnel
1
, a defective molding such as a wrinkle or a crack is generated in the neighborhoods of the ends of the protrusions
9
at the side of the seal edge surface
2
.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to improve the constitution of the protrusions formed on the inner wall of the funnel for preventing the turn of the getter mounting body, thereby to effectively smooth the flow of the molten glass in the neighborhoods of the protrusions when the funnel is molded, and to prevent the generation of the defective molding such as a wrinkle or a crack.
To attain the object above, the present invention provides a funnel for a cathode ray tube, comprising a seal edge surface provided for sealing a panel, a side wall portion gradually decreasing in diameter in a direction from the seal edge surface to a neck tube side, an anode button sealed on an inner wall of the side wall portion to which a getter mounting body comprising a getter and a mounting member is attached, and at least a pair of protrusions formed for restricting the getter mounting body from turning around the anode button from both sides, wherein each of the protrusions continues to the inner wall of the side wall portion as forming slopes from the most protruded part thereof toward the seal edge surface side and the neck tube side, and an inclination of the slope at the seal edge surface side is smaller than an inclination of the slope at the neck tube side.
With this constitution, because the inclination of the slope at the seal edge surface side is smaller than the inclination of the slope at the neck tube side for the most protruded parts of the protrusions, the following advantages are gained when the molten glass moves up on the part corresponding to the side wall portion toward the seal edge surface in the previously described process for molding the funnel. That is, even when there is a difference in the flow speed between the molten glass flowing on the part corresponding to the most protruded parts on the protrusions and the molten glass flowing on the part corresponding to the inner wall in the neighborhood of the protrusions, which are not protruded, one of the molten

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