Electric lamp and discharge devices – With gas or vapor – Incandescent filament lamp
Reexamination Certificate
2001-12-27
2003-11-25
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
With gas or vapor
Incandescent filament lamp
C313S623000, C313S271000
Reexamination Certificate
active
06653782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to selection of material for a fuse/safety switch in a halogen incandescent lamp. The fuse includes a metallic conductor that operates with no degradation during normal operation of the lamp and will burn out, oxidize or fail to conduct during gas changes when the outer bulb is broken. The halogen incandescent lamp includes a burner having a filament with one or both ends that are extended outside the burner through its press seals. More particularly, the extended filament ends outside the burner act as fuses or safety switches when the burner is mounted in a sealed outer envelope. The fuse/safety switch construction renders the lamp inoperable upon breach of the outer envelope and eliminates the fire hazard associated with the operation of the exposed halogen burner.
2. Discussion of the Prior Art
Safety of lamps is paramount in lamp design to protect the user from lethal and potentially destructive sources that may be present when a lamp is partially fractured. In lamps consisting of a light emitting and self contained sealed inner tube, such as a halogen incandescent burner, where electrical conduction is through an outer bulb plus base assembly, the lamp may be partially broken and still operational.
Halogen incandescent lamps consisting of an inner “halogen burner” within a sealed outer have been introduced and are more efficient than conventional incandescent lamps.
FIG. 1
shows a known halogen incandescent burner or capsule having a tungsten filament
10
with a barrel
16
between a pair of tungsten legs
18
, and a “double ended” quartz envelope
20
, with a pinch seal or press
22
at each end. The barrel
16
is located in a central or burner cavity
24
, and the coil ends or legs
18
extend into the presses
22
and are each welded to one end of a molybdenum foil
26
. Molybdenum current supply leads
28
are welded to the other end of the respective molybdenum foils
26
and extend out of the presses
22
.
To facilitate welding of the tungsten coiled legs
18
to the molybdenum foils
26
, a small metal foil (platinum)
26
A may be placed between the tungsten coil legs
18
and the molybdenum foil
26
. The press
22
contains the molybdenum foil
26
, the platinum foil
26
A, as well as the ends of the respective tungsten coil legs
18
and the molybdenum current supply leads
28
. The molybdenum foils
26
are required in the quartz envelope
20
to create a gas-tight seal in the presses
22
over the operating temperatures of the burner
5
. Other burners use mechanical clamps instead of molybdenum foils to electrically attach the tungsten coil legs to the molybdenum current supply leads, where the clamps are located in the press seals and/or the central/burner cavity as described in U.S. patent application Ser. No. 09/606,396, which is incorporated herein by reference.
FIG. 2
shows the filament
10
used in the halogen burner shown in FIG.
1
. The coiled-coil filament
10
has a primary coil
14
and a secondary coil
16
. The filament
10
is formed with a tungsten wire
12
wound on a primary mandrel having a diameter on the order of 80-150 &mgr;m to form the primary coil
14
having an external diameter on the order of 100-300 &mgr;m. The primary coil
14
is wound on a secondary mandrel having a diameter on the order of 300-800 &mgr;m to form the secondary coil
16
which forms the barrel
16
. The secondary mandrel is retracted or dissolved, and the primary mandrel is then removed in whole or in part by dissolving. U.S. Pat. No. 4,132,922 discloses a double-ended burner having a U-shaped fuse and a so-called retained mandrel coil. Portion of the U-shaped fuse is embedded in the press seals while another portion is in the burner.
Double-ended quartz burners are marketed in thin-glass outers, such as blown glass reflectors, decorative outers and the like for general lighting applications. Double-ended quartz burners or capsules
5
with coil legs
18
extending into the presses
22
, as shown in
FIG. 1
, have passive extinction of electric arc at end-of-life.
There is a need to eliminate non-passive failures in hard-glass halogen burners to enable marketing of thin-glass outer lamps containing the hard-glass burner. Further, there is a need to reduce the cost of lamps and to increase efficiency of manufacture thereof. There is also a need to eliminate molybdenum foils or clamps in the burner as well as eliminating the need for additional elements to form a safety switch or fuse in order to reduce lamp cost, simplify manufacture thereof, and provide a more robust lamp, while preventing lamp operation when the outer lamp envelope is breached.
Further, in a lamp having a self-contained, light emission source mounted in and electrically connected through a sealed outer, there is a need for a safety switch or fuse that will disable operation of the inner arc tube when the hermetically sealed outer is broken. There is also a need to disable power to inner arc tube at the time the hermetic seal is fractured and power applied to the lamp. A further need is to disable electrical conduction of high-voltage differences within the inner volume conductive surfaces prior to application of high current. There is also a need to achieve these safety improvements in lamps with vacuum or sub-atmospheric pressure, such as anaerobic gas for example between the inner and the outer. There is a further need to reduce the cost of double ended burners, such as made from quartz. There is also a need for reduction of stress within the press seal and metal conductor interface.
There is a further need for improvement of manufacturing efficiency, and dealing better with exhaust tubes, such as selling the exhaust tube with the lamp. There is a need for a protective layer over the fusing material to prevent ignition of nearby material in a “cheese cloth” test. There is also a need for an arc tube design with a dominant passive failure mechanism at the end-of-life.
SUMMARY OF THE INVENTION
According to the invention, a halogen incandescent capsule or burner, which may be double-ended or single-ended, has an envelope, such as a hard-glass or quartz envelope, forming an inner/burner cavity. Illustratively, the burner is surrounded by an external envelope attached to a base to form a lamp. At least one end of the burner has a press. A filament, e.g. a tungsten filament, is included in the inner cavity. At least one leg of the filament is modified, e.g., stretched, extended, uncoiled for a coiled filament or never wound, to extend out of the press for electrical attachment, by welding for example, to lamp current supply leads in an outer/lamp cavity between the burner and the external envelope of the lamp. For a double-ended burner, one or both legs of the filament may be modified to extend out of one or both of the presses, while for a single-ended burner, one of the legs of the filament is modified to extend out of the press. The lamp cavity is evacuated and filled with a non-oxidizing gas at less than one atmosphere of pressure.
The tungsten wires that extend out of the burner and are connected to the current supply leads in the outer cavity act as fuses or safety switches, thus eliminating the need for additional elements to form a fuse or to form lead wires and foils in the presses.
When the filament fails at end-of-life, the arc is extinguished passively with disintegration of the filament leg in the inner cavity and/or near the inside surface of the presses.
According to a further aspect of the invention, the filament has a primary coil, where the primary coil of the filament leg is modified so that the leg portion in the press is straight or has an increased pitch. The extended coil leg reduces the extinction time and electric arc energy at the end-of-life due to reduced linear wire density near the pinch. Further, the portion of the stretched-out tungsten leg outside the burner, i.e., in the outer/lamp cavity acts as a fuse or safety switch. In particular, upon breach of the outer or external lamp envelop
Vallabhaneni Eswara V.
Woods Joseph P.
Macchiarolo Peter
O'Shea Sandra
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