Television – Video display – Cabinet or chassis
Reexamination Certificate
1998-10-02
2001-09-11
Brown, Peter R. (Department: 3636)
Television
Video display
Cabinet or chassis
C312S007200, C312S223200, C312S409000
Reexamination Certificate
active
06288759
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from Korean Patent Application No. P97-50853, filed on Oct. 2, 1997 and entitled Display Apparatus with a Double Cabinet Structure, Korean Utility Model Application No. 98-4163, filed on Mar. 30, 1998 and entitled Display Apparatus Having an Anode Cover for Fire Protection, Korean Utility Model Application No. 98-4164, filed on Mar. 20, 1998 and entitled Shield Device for Video PCB Having a Cap Portion, and Korean Patent Application No. 98-24292, filed on Jun. 26, 1998 and entitled A Display Device Having a Cabinet for Preventing Fire, all filed with the Korean Industrial Property Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CRT-type display device, and more particularly, to a display device having a shield case (inner cabinet) which provides shielding against electromagnetic interference (EMI) and contains a fire which may break out in the interior of the shield case (inner cabinet).
2. Description of the Related Art
Referring to
FIG. 1
, a typical CRT-type display device is largely comprised of: a cathode ray tube (CRT)
20
by which an image is displayed according to a display signal transmitted along with an electric energy; a circuit board
30
mounted on the rear side of the CRT
20
, to control electrical power, the display signal and related circuitry; a front case
10
to which the CRT
20
is mounted; and a rear case
50
which is combined with the front case
10
to encase the interior of the display device. The circuit board
30
is mounted on a circuit board frame
40
which is secured to the front case
10
or the CRT
20
. A bottom frame
90
is mounted to the bottom of the circuit board frame
40
, and a stand (not shown) is generally provided under the bottom frame
90
for support of the entire display device.
In order to provide EMI shielding for such a display device, a shield case
60
is attached to the rear of the CRT
20
and the top of the circuit board
30
to thereby cover these areas and thus minimize the radiation of electromagnetic waves generated by the display device as well as to protect the display device from external electromagnetic interference. As a rule, display devices having screens smaller than fourteen inches do not employ this shielding.
As shown in
FIGS. 2A and 2B
, the shield case
60
is formed of a top plate
60
a
, a pair of lateral plates
60
b
formed on two sides of the top plate
60
a
, and a rear plate
60
c
forming the rear surface of the top plate
60
a.
The shield case
60
is generally cut out of a flat piece of sheet metal to form panel-like sections and then stamped into the desired shape. Therefore, when assembled, the shield case
60
tends to have gaps
65
where the respective plates meet and where complete enclosure is considered unnecessary since the shield case
60
is primarily for EMI shielding purposes only. A plurality of cooling holes
61
are formed throughout many surfaces of the shield case
60
at predetermined locations, to reduce weight and to allow air to circulate within the interior of the shield case
60
, while maintaining adequate shielding effects.
As a significant feature of the shield case
60
, an anode cap shield
62
is provided in a surface of the top plate
60
a
and protrudes upwardly from the surface to a fixed height determined by the presence of an anode cable
32
connecting an anode cap
31
through which high voltage passes to the circuit board
30
to the CRT
20
. Since there is a potential for electrical contact between the anode cap shield
62
and the high-voltage components, an insulating sheet
80
may be installed using notched slots
81
on the underside of the anode cap shield
62
to promote safety.
The anode cap shield
62
is formed of a separately cut and stamped panel attached to the top plate
60
a
, resulting in the formation of openings
63
on either side thereof. Even though the openings
63
may be large and a measurable degree of electromagnetic emission escapes through the openings, the shield case
60
can still meet the prescribed shielding requirements.
The entire assembly shown in
FIG. 2B
is fixed to adjacent coupling components, e.g., the CRT
20
or CRT bracket (not shown) and the circuit board frame
40
, using coupling means such as a hook and groove structure or sheet metal screws. In so coupling, many open portions
64
are present due to weight reduction goals and component access considerations.
Although EMI requirements are met by installing the shielding case
60
constructed as above in a CRT-type display device, in order to meet fire safety standards such as those set by Underwriter's Laboratories (UL) (e.g., UL Standard 1418 (1992), Standard for Safety for Cathode Ray Tubes), the rear case
50
, and sometimes the front case
10
, must be manufactured from fireproof material. That is, if a fire should break out within the interior of the display device, the shielding case
60
offers no protection from the possibility that the fire should spread outward from the device and into the surrounding room. Thus, the rear case
50
should be designed to contain an accidental fire.
In manufacturing and adopting cases made of fireproof material, there is no particular structural problem. However, there is a drawback in that the case, being made of fireproof material, is costly. Besides fireproof material, UL safety requirements stipulate additional measures, for example, the size, shape, position and number of outer cabinet cooling holes. It should therefore be appreciated that when UL requirements are placed on the design of the case, which constitutes the overall appearance of the product, the fundamental design of the entire product, as it appears to the consumer, is restricted.
In addition, the extensive use of fireproof material presents an environmental hazard and is a continual draw on natural resources.
SUMMARY OF THE INVENTION
Accordingly, in order to overcome such drawbacks in the conventional art, it is therefore an object of the present invention to provide a display device in which a shielding case material itself meets fire safety requirements in addition to providing EMI shielding.
It is another object of the present invention to provide a display device having a reduced fabrication cost.
It is yet another object of the present invention to provide a display device in which the outer case design is not restricted by fire safety requirements.
It is still another object of the present invention to provide a display device which promotes environmental concerns.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve these objects and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, there is provided a display device including: a front case; a cathode ray tube mounted on the front case; a main circuit board mounted on the rear side of the cathode ray tube; a circuit board frame, mounted to one of the front case and the cathode ray tube, to support the circuit board; a nonflammable and fire-retardant shield case (inner cabinet) to contain a fire that may break out in the interior of the display device, while providing a shielding effect which minimizes the radiation of electromagnetic waves generated by the display device and protects the display device from external electromagnetic interference; and a rear case that is combined with the front case to encase the interior of the display device.
As a characteristic feature of the present invention, the front and rear cases are made of non-fireproof plastic, yet a display device which meets UL fire safety requirements is provided.
REFERENCES:
patent: 4508640 (1985-04-01), Kanda et al.
patent: 4596670 (1986-06-01), Liu
patent: 4643493 (1987-02-01),
Cho Nam-il
Choi Kwang-Moon
Kim Gwang-hyeon
Kim Tae-hwan
Brown Peter R.
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
Tran Hanh V.
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