Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Reexamination Certificate
2001-04-19
2004-04-20
Glick, Edward J. (Department: 2882)
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
C313S402000, C313S407000, C313S408000
Reexamination Certificate
active
06724137
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to color cathode ray tubes, and more particularly, to a tension mask frame assembly for a color cathode ray tube, having an improved tension mask which is fixed to a frame.
2. Description of the Related Art
In color cathode ray tubes (color CRTs), an electron beam emitted from an electron gun lands on a fluorescent film through electron beam passing holes in a shadow mask and excites the fluorescent film to form an image.
The screen surface of conventional color CRTs which form an image as described above is designed so as to have a predetermined curvature in consideration of the deflection trajectory of an electron beam which is emitted from an electron gun and deflected by a deflection yoke. The tension mask is designed so as to have a curvature corresponding to the curvature of the screen surface.
A shadow mask, which is manufactured so as to have a curvature similar to the curvature of the inner surface of the screen surface, is heated by an electron beam, that is, by a thermoelectron, emitted from the electron gun, which causes a doming phenomenon in which the shadow mask is swollen toward a panel. The doming phenomenon prevents the electron beam from accurately landing on the fluorescent film. As described above, the screen surface is designed to have a predetermined curvature, such that the view angle is narrowed and the fluorescent film is excited at the periphery of the screen surface, thus distorting the formed image.
In order to solve these problems, a color cathode ray tube (CRT) having a flat-surface screen has been developed. In such a color CRT, a tension mask, in a state where a tensile force is applied thereto, is fixed to the inner surface of a panel so as to be separated by a predetermined distance from a fluorescent film formed on the inner surface of the panel. In this state, the panel is sealed with a funnel on which an electron gun and a deflection yoke are mounted.
Examples of a tension mask installed in a color CRT are respectively disclosed in U.S. Pat. No. 5,488,263, U.S. Pat. No. 4,973,283, U.S. Pat. No. 4,942,332, U.S. Pat. No. 4,926,089 and U.S. Pat. No. 6,097,142, for example.
An example of a tension mask, illustrative and exemplary of those disclosed in the aforementioned patents, is shown in FIG.
1
. As shown in
FIG. 1
, the tension mask
20
has a plurality of strips
21
formed in parallel, and a slot
23
is formed by strips
21
and tie bars
22
having a vertical pitch PV, which connect the strips
21
to each other. Here, the vertical pitch PV of the tie bar
22
and the horizontal pitch PH of slots
23
are equal at the center portion of the tension mask
20
to those at the peripheral portion of the tension mask
20
. The slots
23
have a plurality of auxiliary tie bars
24
which extend from a strip
21
on one side to an opposite strip side.
However, in a tension mask
20
having the auxiliary tie bars
24
as described above with respect to
FIG. 1
, as the vertical pitch PV of the tie bar
22
is relatively increased, a ligament ratio is correspondingly lowered. That is, referring to
FIG. 2
, the ligament ratio obtained by dividing the width W of the tie bar
22
by one of two equal parts PV into which the vertical pitch of a slot is divided. Thus, as the vertical pitch of a slot increases, the ligament ratio is relatively lowered.
As described above, when the ligament ratio is lowered, a supporting force between strips
21
is typically deteriorated, so that the tension mask
20
can be easily plastic-deformed by an impact applied from an external source, such as an impact applied in a vertical direction. That is, referring to
FIGS. 1 and 2
, a vibration, which is transmitted from the center to the periphery of the tension mask
20
when an impact is applied in the vertical direction of the tension mask
20
, can cause a sudden increase in stiffness at a relatively-wide end strip area, which is the horizontal end of the tension mask
20
, so that the edge of the tension mask is 20 plastic-deformed. This phenomenon occurs since an impact applied to the center portion is transmitted to the horizontal edge without reduction due to the fact that the vertical pitch of the tension mask
20
is the same at the center portion and the peripheral portion.
U.S. Pa. No. 4,926,089 to Moore, entitled Tied Slit Foil Shadow Mask With False Ties, discloses a front assembly for a color cathode ray tube that includes a glass faceplate that has on its inner surface a centrally disposed phosphor screen. A metal foil shadow mask is mounted in tension on a mask support structure located on opposed sides of the screen. The mask includes a series of parallel strips separated by slits, the strips being coupled by widely spaced ties. The mask has, between the strips, one or more false ties extending partially between, but not interconnecting, adjacent strips. The screen may also have spaced ties interconnecting the grille lines with a periodicity much smaller than that of the mask ties and below an observer's resolution threshold at normal viewing distances.
U.S. Pat. No. 4,942,332 to Adler et al., entitled Tied Slit Mask For Color Cathode Ray Tubes, discloses a slit-type foil tension mask and associated front assembly for a color cathode ray tube that includes a series of parallel strips separated by slits. The strips are loosely coupled by widely spaced ties, the wide tie spacing being such as to produce a strip coupling which promotes handleability of the mask during mask and tube fabrication, and which facilitates damping of strip vibration when mounted in a tube. Also, in
FIG. 11
therein, it is disclosed that the vertical position, or pitch, of the ties is not constant but is randomly varied from tie to tie to suppress tie visibility. Also, in
FIG. 12
therein, it is disclosed that false ties are placed along the slit edges at regular intervals between the real ties and with a pitch less than that of the real ties.
U.S. Pat. No. 4,942,333 to Knox, entitled Shadow Mask With Border Pattern, discloses a shadow mask adapted for tensioned mounting in a flat faced color CRT having a pattern of slits in the border regions of the mask disclosed to provide uniform distribution of tensile stresses across the mask when mounted in the CRT.
U.S. Pat. No. 4,973,283 to Adler et al., entitled Method Of Manufacturing A Tied Slit Mask CRT, discloses a slit-type foil tension mask and associated front assembly for a color cathode ray tube including parallel strips separated by slits. The strips are loosely coupled by widely spaced ties, the wide tie spacing being such as to produce a strip coupling which promotes handleability of the mask during mask and tube fabrication, and which facilitates damping of strip vibration when mounted in a tube.
U.S. Pat. No. 5,072,150 to Lee, entitled Shadow Mask Assembly for Color Picture Tube, discloses a shadow mask frame for a color picture tube that has side walls which are cut out to form cut-out sections, leaving only a plurality of bridge portions. A separate supporting means for the frame is provided in direct contact with the shadow mask.
U.S. Pat. No. 5,126,624 to Ji, entitled Color Cathode Ray Tube Having Improved Spring Type Contactor, discloses a color cathode ray tube having a spring type contactor. The spring type contactor effects electrical connection between a frame and a conductive coating deposited on the inner surface of the funnel, and comprises an ‘.OMEGA.’ shaped fitting portion for being inserted into holes respectively perforated on the shield and the frame so as to be locked therein, a pair of legs abutting the edge of the hole of the shield, and a ‘C’ shaped contact portion extending from one of the legs to contact the conductive coating on the inner surface of the funnel.
U.S. Pat. No. 5,210,459 to Lee, entitled Shadow Mask Structure Of A Color Cathode Ray Tube, discloses a cathode ray tube with a shadow mask, the shadow mask structure being suspended and fixed behind the panel of the cathode ray tube. Plate spring
Choi Sang-Shin
Jeon Sang-Ho
Kim Chan-Yong
Shin Soon-Cheol
Glick Edward J.
Samsung SDI & Co., Ltd.
Yun Jurie
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