GB2240659A

GB2240659A - Shadow mask assembly

Info

Publication number: GB2240659A
Application number: GB9002117A
Authority: GB
Inventors: Chul-Soo Kim
Original assignee: Samsung Electron Devices Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 1990-01-31
Filing date: 1990-01-31
Publication date: 1991-08-07
Also published as: GB9002117D0

Abstract

In a shadow mask frame assembly for a color cathode ray tube, an outwardly extended flange 21 is provided around the front edge of the frame 20, and a welding girth 10d is provided along the edges of the shadow mask 10 at a position matingly facing to the flange 21 and disposed in substantially the same plane as that of the shadow mask beam passing plate. Further, a reinforcing ridge loo is preferably provided between the edge of the beam passing plate and the welding girth 10d. The arrangement facilitates the welding together of the shadow mask and frame while reducing stresses and deformations in the assembly. <IMAGE>

Description

SHADOW MASK FRAME ASSEMBLY FOR COLOR CATHODE RAY TUBE The present invention relates to a shadow mask frame assembly for a color cathode ray tube, and particularly to a shadow mask frame assembly for a color cathode ray tube in which the coupling structure between the shadow mask and the frame is improved.

As shown in Figures 1 and 2, the shadow mask frame assembly which is installed alongside the inner surface of the panel 4 of the usual color cathode ray tube is constituted such that numerous beam passing holes ib are formed in a beam passing plate Ia of a shadow mask 1, and a frame 2 supports the shadow mask 1, while a skirt portion ic is formed along the edges of the shadow mask 1 in such a manner that the sides 2a of the frame should be surrounded by the skirt portion ic. In such a conventional shadow mask frame assembly, the shadow mask and the frame are manufactured by respective press processing, but, because the thickness of the shadow mask is very thin, the shadow mask is very much deformed during the press processing.

Particularly, severe baking deformations occur at the corners where the two skirt plane and the beam passing plane meet one another, with the result that the nearby beam passing holes undergo severe abnormal deformations in addition to the wild deformations occurring to the corner portions. Further, in severer cases, partial disruptions and cleavings occur, and, even in the case where a disruption does not occur, highly strong stresses are concentrated at the corner portions, with the result that, upon deformation of the shadow mask due to the impacts of the electron beams during the operation of the CRT, thermal deformations occur, thereby deteriorating the image quality of the cathode ray tube.

The above described thermal deformations aggravate the doming phenomenon which occurs naturally on the shadow mask during the operation of the cathode ray tube, and therefore, it is necessary that the residue stresses created during the forming of the shadow mask and causing the above described problems be kept to the minimum.

Meanwhile, the "spring back phenomenon" which occurs to the skirt portion due to the press forming is another problem which can not be overlooked. That is, for the shadow mask is reguired to be precisely and securely fixed to the frame, first the skirt portion which constitute the periphery of the shadow mask has to be normally formed, whereas, in most cases, the skirt portion can not closely surround the side faces of the frame due to the spring back phenomenon of the skirt portion. Thus, if gaps come into being between the skirt portion and the side faces of the frame, then there is the apprehension that the position of the shadow mask relative to that of the frame can be displaced, and that the exact positions to be welded can not be identified during the welding process, thereby making the welding task very difficult.

Therefore it is the object of the present invention to provide a shadow mask frame assembly for a color cathode ray tube in which the abnormal deformation of the shadow mask occurred during the press forming is kept to the minimum, to such extent that a perfect assembly between the shadow mask and the frame should be possible, thereby improving the quality of the cathode ray tube.

In achieving the above object, the shadow mask frame assembly for a color cathode ray tube according to the present invention comprises: a shadow mask having numerous beam passing holes; and a frame for supporting the shadow mask, characterized in that an outwardly facing flange is provided along the front edge of the frame which is to be welded to the shadow mask, and that a welding girth is provided along the edge of the shadow mask on a substantially same plane as the beam passing plane and at a position matingly facing to the flange.

The above object and other advantages of the present invention will become more apparent by describing in detail the preferred embodiment of the present invention with reference to the attached drawings in which: Figure 1 is a perspective view of the conventional shadow mask frame assembly; Figure 2 is a sectional view of a part of a cathode ray tube in which a conventional shadow mask frame assembly is adopted; Figure 3 is an exploded perspective view of the preferred embodiment of the shadow mask frame assembly according to the present invention; and Figure 4 is a sectional view of a part of the cathode ray tube in which the shadow mask frame assembly of Figure 3 is adopted.

As shown in Figure 3, a shadow mask 10 consists of a beam passing plate lOa having countless beam passing holes lOb, a welding girth 10d provided along the edge of the beam passing plate 10a on the substantially same plane as that of the beam passing plate 10a, and a reinforcing ridge lOe provided inwardly to the welding girth lOd and along the edge portion of the beam passing plate 10a. A flange 21 is extended along the edge of a frame 20 in a rectangularly bent direction therefrom to which the shadow mask 10 is to be coupled. An ordinary inner shield 30 for shielding the geomagnetic field is provided at the side of the frame 20 oppositely from the position of the shadow mask 10.

As shown in Figure 4, the above mentioned components are coupled in such a manner that the shadow mask 10 is secured to the frame 20 by welding the welding girth 10d to the flange 21 of the frame 20. That is, the rectangularly bent conventional skirt is removed from the shadow mask 10, and instead, a welding girth 10d is provided to the shadow mask 10 on the same plane as that of the body of the shadow mask 10, so that the welding girth can be coupled with and welded to the frame 20, while the shadow mask 10 is reinforced in its strength owing to the reinforcing ridge 10e provided along the edge portion thereof.

In the shadow mask frame assembly according to the present invention described above, the shadow mask is pressformed through a step of spherically forming the beam passing plate, and a step of forming the reinforcing ridge along the periphery of the beam passing plate, and therefore, the stress is not concentrated at a particular portion unlike in the conventional methods. That is, no skirt is formed unlike in the case of the conventional methods, and the stress is uniformly distributed over the whole face of the beam passing plate, with the result that the twisting of its body and the swelling of the beam passing plate liable to occur due to the concentration of the stress after the thermal expansion through the impacts of the electron beams can be greatly reduced.

Further, the shadow mask frame assembly can be securely and precisely coupled, and the welding task as the coupling process can be conveniently carried out because the frame body which is low in the thermal expansion and the spring back phenomenon is provided with a flange to which the welding girth of the shadow mask can be welded.

Claims

CLAIMS:

1. A shadow mask frame assembly for a colour cathode ray tube comprising: a shadow mask having numerous beam passing holes in a beam passing plate thereof; and a frame for fixedly supporting said shadow mask, characterized in that an outwardly extended flange is provided along the front edge of said frame to the side where said shadow mask is weld-fixed, and that a welding girth is provided along the edges of said shadow mask at a position matingly facing said flange and on a substantially same plane as that of said beam passing plate.

2. A shadow mask frame assembly for a color cathode ray tube as claimed in claim 1, wherein a reinforcing ridge is provided between the edge of said beam passing plate and said welding girth.

3. A shadow mask frame assembly for a color cathode ray tube, substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.

4. A shadow mask assembly for a colour cathode ray tube, comprising an apertured shadow mask and a frame to which the periphery of the shadow mask is attached, wherein the attachment of the shadow mask to the frame is by way of respective peripheral flanges thereof fixed together face-to-face and extending in or parallel to the general plane of the shadow mask.

5. A shadow mask frame assembly substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.