Electric lamp and discharge devices – Electrode and shield structures – With lead wire or connector
Reexamination Certificate
2002-01-03
2004-06-29
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Electrode and shield structures
With lead wire or connector
C313S242000, C313S240000, C313S492000, C313S572000
Reexamination Certificate
active
06756723
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fluorescent lamp, a method for manufacturing the fluorescent lamp and a fluorescent lamp device and preferably, to a fluorescent lamp which can cope with its lamp life end in a high frequency operation. More particularly, the present invention relates to a fluorescent lamp which can suppress melting of stem glass when inner lead wires of a stem are discharged as electrodes and can prevent short-circuiting between the inner lead wires caused by adhesion or deposition of spattering material produced by vaporization of filaments and inner lead wires, a method for manufacturing the fluorescent lamp and a fluorescent lamp device.
When a high frequency power is applied between counter electrodes of a fluorescent lamp to light the lamp, a phenomenon unique to lamp life (the lamp reaches its life end when the lamp has been operated for an accumulated time of several thousands of hours) end takes place. When the lamp comes to the end of the life and emitter material coated on filaments disappears, the lamp usually cannot come on and comes to its life end. However, even when the emitter of the filaments becomes null, there may occur such an unexpected situation that discharge is maintained with the filaments having the emitter already disappeared or inner lead wires being acting as hot spots. In this case, when discharge is maintained with, in particular, the inner lead wires acting as the hot spots, a discharge current larger than its rated value flows through the lead wires. For this reason, the lead wires may melt and eventually its stem may be thermally melted, which operation is called a first operation mode.
Further, in another life end mode of the fluorescent lamp, the material (W) of the filaments, the emitter material (BaO, etc.) coated on the filaments and the material (Ni, Fe) of the inner lead wires spatter and adhere or deposit onto tip end faces of flare stems close to the filaments. In particular, at the end of the lamp life, these substances tend to spatter and adhere or deposit onto the tip end face of each of the flare stems. The above adhesive or deposit, which is electrically conductive, may establish an electric path and energized when deposited. More specifically, the spattered material adhered and deposited on the tip end face of the flare stem may establish an electric path on the surface of the flare stem between a pair of electrically-isolated inner lead wires, thus leading to electric conduction between the inner lead wires. In such a case, a current flows through the electric path to heat the flare stem surface, which disadvantageously results in over-heat damage of the flare stem or in a large wattage loss due to short-circuiting. Such an operation mode is called a second operation mode.
The invention for overcoming the problem with the second operation mode is disclosed in JP-A-6-338289 Publication (referred to as the known citation 1, hereinafter), which will be briefly explained below.
FIGS. 1A
to
1
C shows an embodiment of a lamp disclosed in the known citation 1, wherein
FIG. 1A
is a cross-sectional view of the lamp,
FIG. 1B
is a cross-sectional view of the lamp taken along line A—A in
FIG. 1A
, and
FIG. 1C
is a cross-sectional view of the lamp taken along line B—B in FIG.
1
A. As shown in
FIG. 1B
, a recess
202
is made in a flare stem at at least one of root parts of a pair of inner lead wires
201
(The recess is made only at one lead wire in the drawing). In
FIG. 1C
, reference numeral
203
denotes an exhaust hole of an exhaust tube in the flare stem. Also disclosed in the citation 1 is that the recess may be made in an intermediate part
204
of the flare stem. Such a recess functions as a drop place. With such an arrangement, at the end of the lamp life, substance spattered from the electrode deposits on the flare stem. However, there is such a description in the citation that the presence of the recess functioning as the drop place makes it difficult for the substance to deposit only on that recess area, thus preventing establishment of an electric path and avoiding an electric short-circuiting between the pair of lead wires.
FIG. 2
is an alternate of the arrangement of
FIG. 1
disclosed in the citation 1. In the drawing, the same reference numerals as those in
FIG. 1
denote the same parts. The arrangement of
FIG. 2
is different from that of
FIG. 1
in that the recess
202
is replaced by such an insulation tube
205
as to surround the neighborhood of a sealing part of at least one of the inner lead wires
201
(The insulation tube
205
is provided only one lead wire in the drawing). With such an arrangement, the above spattered substance can deposit on the flare stem but less deposit on the inner lead wires
201
in the vicinity of the sealing part, thus blocking formation of the aforementioned electric path.
FIG. 3
shows another alternate of the arrangement of
FIG. 1
disclosed in the citation 1. In the drawing, the same reference numerals as those in
FIG. 1
denote the same parts as those in
FIG. 1. A
difference between the arrangement of FIG.
3
and that of
FIG. 1
is that the recess
202
in
FIG. 1
is replaced by an overhanging member
206
which is provided only for at least one of the pair of inner lead wires
201
(In the illustrated example, the overhanging member
206
is provided only one lead wire). There is such a description in the citation that, with such an arrangement, the aforementioned substance can deposit on the flare stem but the amount of substance deposited onto the inner lead wire
201
in the vicinity of the sealing part can be reduced, thus suppressing formation of the aforementioned electric path.
One of the related citations is JP-A-6-140000 Publication. The citation discloses an arrangement in which, as shown in
FIG. 4
, a glass bead
101
is fixedly mounted to a pair of lead wires
102
. This enables reduction of an oxidizing rate of the lead wires and avoidance of an extremely short life of a fluorescent lamp. With such an arrangement, the presence of the glass bead
101
enables reduction of the amount of deposit spattered onto the lead wires
102
and onto an area
110
on the flare stem. However, since the above spattered deposit substance deposits on the glass bead
101
, a short-circuiting may disadvantageously take place between the pair of lead wires through the deposit on the glass bead
101
. In the drawing, reference numeral
105
denotes a bead mount, numeral
106
denotes a filament coil,
105
denotes a bead mount,
109
denotes an exhaust tube.
One of the related citations is JP-A-3-81950 Publication. The citation describes the aforementioned first operation mode. As an arrangement of overcoming the problem with the first operation mode, an arrangement of
FIG. 23
is disclosed therein.
FIG. 23
shows an arrangement in the vicinity of a lamp electrode. A button stem
27
is air-tightly joined to an end of a glass bulb
21
by means of an adhesive agent (not shown). Provided to the button stem
27
is a support rod
29
, on which a heat shielding plate
30
is mounted. The heat shielding plate
30
, which is disposed between an electrode
26
and stem
27
, is made of heat-resistive metal such as stainless material. The heat shielding plate
30
, which is shaped into a trough, covers a rear side of the electrode
26
. Numerals
28
a
and
28
b
denote lead wires respectively. Such a description is disclosed in the citation that, with such an arrangement, even if the above first operation mode phenomenon takes place, the possibility of over-heat damage of the button stem
27
can be reduced because of the heat shield.
One of the related citations is JP-A-54-44372 Publication. The citation is directed to an improvement in an interior
2
of a fluorescent lamp
1
, in which, as shown in
FIG. 24
, a circular heat shielding plate
13
is provided between a filament
12
and a base
9
to use the base
9
as a coolest point and to prevent heat radiated from the filament
12
from transmitting to the base
9
. I
Fukushima Mamoru
Kobayashi Yasuo
Ogawa Soichiro
Hitachi , Ltd.
Patel Ashok
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