Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
1999-10-05
2001-04-10
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C313S407000, C313S402000
Reexamination Certificate
active
06213836
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cathode ray tube that irradiates an electron beam utilizing high voltage and to a method for manufacturing the same. More particularly, the present invention relates to a cathode ray tube having an inner magnetic shield and to a method for fixing the inner magnetic shield to the cathode ray tube.
BACKGROUND OF THE INVENTION
In order to improve pressure-resistant characteristics and to prevent electric discharges caused by a foreign material produced by welding sparks in fixing an inner magnetic shield to a frame (a shadow mask frame) of a cathode ray tube by welding, a method for fixing an inner magnetic shield to a frame using spring fixing members (hereafter referred to as fixing members) has been proposed as disclosed, for example, in Japanese laid-open patent application (Tokkai Hei)
5-151908.
That is, the frame and the inner magnetic shield have a first and a second flange portion projecting in the direction crossing the tube axis of the cathode ray tube at right angles, respectively. About 10 engagement holes whose diameter is 10 mm or less are provided on each side of the first and second flange portions. Generally &OHgr;-shaped fixing members are firmly fit into the engagement holes, thereby fixing the inner magnetic shield to the frame by utilizing spring elasticity. According to this method, since the inner magnetic shield can be fixed without welding, electric discharges caused by a foreign material produced by welding sparks can be prevented.
Conventionally, in consideration of mass-productivity, etc., an inner magnetic shield has been manufactured by punching a sheet by a press. In the case of the press working, burrs are produced on an end face of a part being punched in punching a sheet. Generally, the material for a fixing member is harder than that for an inner magnetic shield. Therefore, burrs on an end face of an engagement hole on an inner magnetic shield drop off when a fixing member comes into contact with the end face of the engagement hole in fitting the fixing member into the engagement hole in order to fix an inner magnetic shield to a frame.
When burrs that are metal scraps drop off, the burrs are caught in the openings of a shadow mask and the openings may be closed. Even if the burrs are not directly caught in the openings of the shadow mask, the burrs may intrude into a slight space between the shadow mask and the frame. The burrs may be come out from the space between the shadow mask and the frame by vibration, impact or the like in the subsequent steps such as, for example, a frit seal process wherein a panel and a funnel are glued, a sealing process wherein an electron gun is installed, an evacuation process wherein a valve is evacuated, and the like. Then, the burrs may be caught in the openings of the shadow mask. When the burrs are caught in the openings of the shadow mask, which causes the openings of the shadow mask to be closed, an electron beam is shielded and the fluorescent substance of the screen does not emit light. That is to say, it causes a picture defect.
In collecting and analyzing the foreign materials that had closed the openings of the shadow mask, about 30% of the foreign materials were burrs that were metal foreign materials. In order to remove burrs, for example, a blasting treatment, chemical polishing, electrolytic polishing and the like have been carried out, since it is not possible to prevent the production of burrs in the press working. In the case of the blasting treatment, there is a problem that an inner magnetic shield is deformed by putting the polishing material on the inner magnetic shield at high pressure. In case of chemical polishing, electrolytic polishing or the like, the processes such as washing, neutralization, washing, etc. are needed after the polishing treatment. If these processes after the polishing are not carried out properly, in the blackening film treatment, which is a surface treatment of the inner magnetic shield carried out in a subsequent process, a nonuniform film in quality may be obtained, the film may drop off or the like. Moreover, many processes for these treatments are needed, which causes cost increases.
SUMMARY OF THE INVENTION
In order to solve the problems mentioned above in the prior art, it is an object of the present invention to provide a cathode ray tube wherein an inner magnetic shield is simply fixed to a frame supporting a shadow mask with fixing members capable of preventing burrs from dropping at the time of fitting the fixing members firmly into the engagement holes provided on the frame and the inner magnetic shield, and a method for manufacturing the same.
In order to achieve the object mentioned above, the cathode ray tube of the present invention comprises: (1) a shadow mask having a plurality of predetermined-shape openings arranged in a predetermined pattern; (2) a frame supporting the shadow mask, which has a first flange portion formed in a direction crossing the tube axis of the cathode ray tube almost at a right angle and a plurality of first engagement holes formed on the first flange portion; (3) an inner magnetic shield fixed to the frame, which has a second flange portion formed in the direction crossing the tube axis of the cathode ray tube almost at a right angle and a plurality of second engagement holes that are formed on the second flange portion and are facing a corresponding first engagement hole of the first flange portion; and (4) a plurality of fixing members fixing the inner magnetic shield to the frame by putting and fitting into the first engagement holes and second engagement holes that are facing each other. In the cathode ray tube mentioned above, at least a part of an end face of the second engagement hole on the inner magnetic shield, where the fixing member slides, is folded back.
In the construction of the cathode ray tube according to the present invention, it is preferable that the width of the folded portion on an end face of the second engagement hole on the inner magnetic shield is 1.0 mm or less.
In the construction of the cathode ray tube according to the present invention, it is preferable that the shape of the first engagement holes on the frame and of the second engagement holes on the inner magnetic shield is one selected from a substantially rectangular shape, a substantially circular shape or a substantially elliptical shape.
The method for manufacturing the cathode ray tube of the present invention is a method for manufacturing the cathode ray tube comprising: (1) a shadow mask having a plurality of predetermined-shape openings arranged in a predetermined pattern; (2) a frame supporting the shadow mask; and (3) an inner magnetic shield fixed in the frame. In the method for manufacturing the cathode ray tube, a plurality of first and second engagement holes facing each other are provided on the first and second flange portions of the frame and of the inner magnetic shield, which are formed in a direction crossing the tube axis of the cathode ray tube almost at a right angle, and at least a part of an end face of the second engagement hole on the inner magnetic shield, where the fixing member slides, is folded back. Then, the fixing members are put and fit into each of the facing first and second engagement holes, thereby fixing the inner magnetic shield to the frame.
In the method for manufacturing the cathode ray tube according to the present invention, it is preferable that the width of the folding portion on an end face of the second engagement hole on the inner magnetic shield is 1.0 mm or less.
In the method for manufacturing the cathode ray tube according to the present invention, it is preferable that the shape of the first engagement holes on the frame and of the second engagement holes on the inner magnetic shield is one selected from a substantially rectangular shape, a substantially circular shape or a substantially elliptical shape.
According to the construction of the cathode ray tube according to the present invention and the method for manufacturi
Ishii Toshio
Morii Masanori
Muramoto Tadashi
Nagata Keiji
Gerike Matthew J.
Matsushita Electronics Corporation
Merchant & Gould P.C.
Ramsey Kenneth J.
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