Electric lamp and discharge devices – With optical device or special ray transmissive envelope – Reflector
Reexamination Certificate
2001-11-27
2004-03-23
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With optical device or special ray transmissive envelope
Reflector
C313S635000
Reexamination Certificate
active
06710521
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a discharge bulb having an arc tube that is a sealed bulb acting as a light-emitting discharge section formed with pinch seal portions on both ends thereof.
2. Description of the Related Art
A conventional discharge bulb is illustrated in
FIG. 9. A
cylindrical shroud glass
3
having an ultraviolet blocking effect is integrally welded to an arc tube
1
. The cylindrical shroud glass
3
covers pinch seal portions
1
a
and
1
b
and a sealed glass bulb
2
that is a light-emitting discharge section. The cylindrical shroud glass
3
is used, in part, to prevent broken pieces of the arc tube
1
from spreading as a result of an explosion, and to eliminate ultraviolet light in a waveband that is harmful to human bodies and the like from the light emitted by the sealed glass bulb
2
. The reference symbol “a” represents electrodes provided in a face-to-face relationship with the sealed glass bulb
2
as a light-emitting section, and the reference symbol “b” represents molybdenum foils sealed to the pinch seal portions
1
a
and
1
b
. The electrodes a and a and the lead wire c are connected to the molybdenum foil b.
The lead wire c extracted from the pinch seal portion
1
a
on the front end of the arc tube
1
is supported by a lead support
6
extending in front of an insulated base
5
, and the rear end of the arc tube
1
is secured to the front side of the insulated base
5
with an adhesive
4
to integrate the arc tube
1
with the insulated base
5
.
The symbol
10
represents a reflector for forming a meeting beam from, for example, a headlamp of an automobile, and symbol
9
represents a shade having a light-blocking section in a configuration adapted to an effective reflecting surface
10
a
of the reflector and is typically provided to guide light emitted by the sealed glass bulb
2
only to the effective reflecting surface
10
a
. The shade
9
also has a function of forming clear-cut lines of a luminous distribution pattern.
In the above-described conventional discharge bulb, since a very large quantity of light is emitted by the sealed glass bulb
2
compared to an incandescent light, a large quantity of light is also guided to the pinch seal portions because of a light-guide effect. For reasons including the fact that the molybdenum foils b that reflect light are normally provided on the pinch seal portions
1
a
and
1
b
, and that the surface configuration of the pinch seal portions is uneven, light can exit the pinch seal portions
1
a
and
1
b
and be reflected by the reflector
10
in the forward direction, which could result in glare.
SUMMARY OF THE INVENTION
In an intention to prevent light from exiting the pinch seal portions
1
a
and
1
b
, the inventors applied light-blocking films, that had generally been used for forming a luminous distribution, to the pinch seal portions
1
a
and
1
b
and to the shroud glass
3
. However, using this technique, new problems arose in that an intended color temperature could not be achieved because of a large increase of the temperature of the pinch seal portions
1
a
and
1
b
and the sealed glass bulb
2
, although light from the pinch seal portions
1
a
and
1
b
is prevented to some degree. In addition, the pinch seal portions
1
a
and
1
b
become likely to crack which reduces the durability of the arc tube. Further, the light-blocking films can come off because of the high temperature in their environment.
The inventors thought that the great increase in the temperature of the arc tube was attributable to the fact that the conventional light-blocking films for forming a luminous pattern blocked infrared light in addition to visible light to accumulate heat in the arc tube. Then, they thought that the accumulation of heat in the arc tube could be avoided by transmitting infrared light while blocking visible light. In experiments, the inventors confirmed that the above-described problems will not occur when infrared transmitting films for blocking visible light and transmitting infrared light are used as the light-blocking films to prevent the overheating of the pinch seal portions
1
a
and
1
b
and the sealed glass bulb
2
, and accordingly, the present invention is being presented based on such a finding.
It is an object of the present invention to provide a discharge bulb that does not produce glare and that has excellent durability by applying infrared transmitting films for blocking visible light and transmitting infrared light to at least pinch seal portions of an arc tube.
In order to achieve the above-described object, a discharge bulb according to a first aspect of the invention includes an arc tube that is a sealed bulb, for example, a glass bulb, as a light emitting discharge section formed with pinch seal portions at both ends thereof, in which infrared transmitting films for blocking visible light and transmitting infrared light are applied to at least the pinch seal portions of the arc tube.
The infrared transmitting films prevent visible light from exiting the pinch seal portions, and therefore suppress generation of light that can result in glare.
Since the infrared transmitting films do not prevent infrared light from exiting the pinch seal portions, no heat is accumulated in the arc tube (in particular, the pinch seal portions and sealed glass bulb).
In a second aspect of the invention, the arc tube of the present invention may be provided in a lighting chamber of a vehicle front light lamp, and the infrared transmitting films may be applied in predetermined ranges extending from the bottom of the sealed glass bulb of the arc tube provided in the lighting chamber to left and right lateral surfaces thereof.
Since substances such as mercury and a metal halide may be enclosed in the sealed glass bulb in a saturated state, the enclosed substances may be deposited in a liquid state on the bottom of the sealed glass bulb. As a result, light exiting the sealed glass bulb downward becomes yellow light that is colored by the enclosed substances, and that light is mixed with white light that should be emitted by the sealed glass bulb, which is not preferable. The infrared transmitting films provided to extend from the bottom of the sealed glass bulb to left and right lateral surfaces thereof prevent the colored light (yellow light) from exiting the sealed glass bulb.
In a third aspect of the present invention, the discharge bulb may be an arc tube that has a sealed glass bulb as a light emitting discharge section formed with pinch seal portions on both ends thereof and a cylindrical shroud glass integrally joined, such as by welding, to the arc tube to enclose and seal the arc tube. Infrared transmitting films for blocking visible light and transmitting infrared light are applied to at least the pinch seal portions of the arc tube and/or at least regions of the shroud glass associated with the pinch seal portions.
The infrared transmitting films provided on the pinch seal portions of the arc tube and/or the shroud glass prevent visible light from exiting the pinch seal portions and prevent visible light that has exited the pinch seal portions from exiting the shroud glass, which suppresses generation of light that can result in glare.
The infrared transmitting films provided on the pinch seal portions of the arc tube and/or the shroud glass do not prevent infrared light from exiting the pinch seal portions and do not prevent infrared light that has exited the pinch seal portions from exiting the shroud glass, which prevents accumulation of heat in the arc tube (the pinch seal portions and sealed glass bulb).
Especially, when the infrared transmitting film is applied only to the shroud glass, accumulation of heat in the arc tube is less likely to occur than when the infrared transmitting film is applied to the pinch seal portions only or to both of the pinch seal portions and the shroud glass because the temperature of the shroud glass is lower than the temperature of the arc tube (pinch seal portions) when the di
Shido Masaya
Tsuda Toshiaki
Koito Manufacturing Co. Ltd.
Patel Vip
Williams Joseph
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