Fluorescent luminous tube

Details Fluorescent luminous tube Fluorescent luminous tube

2002-08-06

2004-11-02

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

With gas or vapor

Having particular electrode structure

C313S491000, C313S631000

Reexamination Certificate

active

06812643

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a fluorescent luminous tube; and, more particularly, to a fluorescent luminous tube having an improved connecting structure for cathode filaments.
BACKGROUND OF THE INVENTION
FIG. 5A
shows a plan view (a partial cross-sectional view) of a conventional fluorescent luminous tube (or fluorescent display device), and
FIGS. 5B and 5C
depict schematic views of a connecting structure for cathode filaments thereof.
Anode electrodes
63
on which a fluorescent material is deposited are formed on an anode substrate
61
made of an insulating material such as a glass. Grids
64
are arranged between the anode electrodes
63
and filaments
60
to control electrons emitted from the filaments
60
to the anode electrodes
63
. The filaments
60
are tightly suspended between an anchor
661
and a support
662
so that a display region
65
is covered. The anchor
661
and the support
662
are fabricated by shaping, e.g., a metal plate, and have three-dimensional shapes. The filament
60
is welded at one end on a resilient filament support member of the anchor
661
and at the other end on a filament support member of the support
662
. The anchor
661
and the support
662
are fixed on the anode substrate
61
and are respectively connected to cathode wirings
671
and
672
functioning as take-out leads. Cathode wirings
671
and
672
can be formed as one body with the anchor
661
and the support
662
, respectively. A reference numeral
62
represents a side plate made of an insulating material, e.g., a glass.
FIGS. 5B and 5C
depict possible arrangements of the display region
65
and the filaments
60
as well as electrical connection of the filaments
60
to the anchor
661
and the support
662
. The filaments
60
can be arranged either in a horizontal direction as shown in
FIG. 5B
or in a vertical direction as shown in
FIG. 5C
depending on a display pattern of the anode electrodes
63
as shown in FIG.
5
A.
If the aspect ratio of the display region
65
is 1:2, the length of a filament
60
in case of
FIG. 5B
is about twice that of a filament
60
shown in FIG.
5
C.
In general, the filaments
60
are fabricated by coating a core wire, made of tungsten or tungsten alloy, with carbonate for emitting thermal electrons. If an electrical current is supplied to the filaments
60
, heat is generated in the filaments
60
due to their own resistance and the carbonate heated by the generated heat emits electrons. The temperature of the filaments
60
is normally maintained at about 600 to 650° C. In case each of the filaments
60
has a thickness of about 0.64 MG (a diameter of about 15 &mgr;m), a current of about 27 mA is required to maintain the filament temperature at about 600 to 650° C. In case where a 0.64 MG filament has a length of 25 mm, its resistance value is about 48 &OHgr;. Accordingly, a filament voltage should be set to be 1.3 V in order to apply the current of 27 mA through the 0.64 MG filament having the length of 25 mm.
Assuming that each filament
60
in
FIGS. 5B and 5C
has the thickness of 0.64 MG and that the length of each of the filaments
60
in case of
FIG. 5C
is 25 mm, each filament
60
in an arrangement shown in
FIG. 5B
will be of a length of 50 mm and, thus, a resistance thereof will be 96 &OHgr;. Therefore, a filament voltage in case of
FIG. 5B
should be set to be 2.6 V, i.e., twice the filament voltage required in FIG.
5
C.
As can be seen from the above, since a power source module having a different voltage should be prepared for every filament having a different length, the cost for the power source modules is increased, which in turn raises the manufacturing cost for the fluorescent luminous tube as well.
FIGS. 6A
to
6
C show various schemes conventionally employed in connecting filaments in series.
FIG. 6A
illustrates an example where three filaments
60
are connected in series, in which two anchors
6611
and
6612
and two supports
6621
and
6622
are provided. The anchor
6611
and the support
6621
are connected to cathode wirings
671
and
672
, respectively, and the anchor
6612
and the support
6622
are employed for making series connection of filaments
60
.
FIG. 6B
offers an example where five filaments
60
are connected in series, in which an anchor
6613
and a support
6623
are added to the structure shown in FIG.
6
A.
FIG. 6C
describes an example where seven filaments
60
are connected in series, in which an anchor
6614
and a support
6624
are further added to the structure illustrated in FIG.
6
B.
As shown in
FIGS. 6A
to
6
C, as the number of the filaments
60
is increased to be 3, 5 and 7, both the number of the anchors and the number of the supports are respectively required to be increased to be 2, 3 and 4, accordingly. As a result, the cost for manufacturing and installing the anchors and the supports and for mounting filaments thereon is increased, resulting in the increase of the whole manufacturing cost for the fluorescent luminous tube. Further, it is difficult to scale-down the anchors and the supports because they are required to have predetermined strength. Accordingly, a footprint for mounting the anchors and supports is increased, so that a dead space other than the display region becomes also increased, hampering the fabrication of a scaled down, thin and light-weighted fluorescent luminous tube.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a fluorescent luminous tube using a single power source for various cathode filaments having different lengths and diameters and employing a connecting structure that allows cathode filaments to be easily connected in series in a reduced installation space.
In accordance with the present invention, there is provided a fluorescent luminous tube including a plurality of cathode filaments; a multiplicity of a cathode wirings, each cathode wiring including one or more terminal portions and a wiring portion and being formed of a metal layer; and one or more intermediate portions, each being made of a metal layer, wherein the cathode filament is grouped into at least one set of one or more filaments and filaments in each set are connected in series by fixing an end portion thereof on a terminal portion or an intermediate portion by ultrasonic wire bonding or ultrasonic bonding.


REFERENCES:
patent: 355151755 (1980-11-01), None

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