Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
2000-06-29
2003-10-28
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
C313S626000, C313S578000
Reexamination Certificate
active
06639364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a halogen incandescent capsule having a light-transmitting envelope which encloses a sealed cavity with a pinch at one end, and a filament having a pair of legs and a central barrel enclosed within the sealed cavity. The ends or legs of the filament are attached to a pair of lead wires which are sealed in the pinch. The lead wires extend out of the sealed cavity from the pinch. More particularly, the invention relates to a capsule having a filament with a primary coil and a secondary coil, where the primary coil ends form the legs for attachment to the leads.
2. Discussion of the Prior Art
FIG. 1
shows a known halogen incandescent 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
22
at each end. The barrel
16
is located in a central cavity
24
, and the coil legs
18
extend into the pinches
22
and are each welded to one end of a molybdenum foil
26
. Molybdenum leads
28
are welded to the other end of the respective molybdenum foils
26
and extend out of the pinches
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 pinch
22
contains the molybdenum foil
26
, the platinum foil
26
A, as well as the ends of the respective tungsten coil legs
18
and molybdenum leads
28
. The molybdenum foil is required in quartz envelopes
20
to create a gas-tight seal in the pinch
22
over the operating temperatures of the capsule.
FIG. 2
shows a conventional single-ended hard-glass capsule with a hard-glass envelope
30
and a pinch
32
at one end. Short and long molybdenum leads
36
,
38
pass through the pinch
32
. The short lead
36
is attached to one of the coil legs
18
typically with a clamp
37
formed in the molybdenum lead
36
. The long lead
38
is attached to the coil leg
18
via clamp
39
, for example. According to this known construction, both of the clamps
37
,
39
as well as the entire tungsten filament
10
are located in the sealed cavity
34
. The coefficient of thermal expansion of the hard-glass matches that of molybdenum eliminating the requirement of the molybdenum foils
26
shown in FIG.
1
. Addition of molybdenum to the interior of the cavity
34
may require modification of the halogen chemistry to attenuate transport of molybdenum from the lead to the bulb wall.
FIG. 3
shows the filament
10
used in the halogen capsules shown in
FIGS. 1 and 2
. 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 capsule having a so-called retained mandrel coil.
Double-ended quartz capsules are marketed in thin-glass outers, such as blown glass reflectors, decorative outers and the like for general lighting applications. Single-ended hard-glass capsules are marketed in thick-glass outers such as parabolic aluminized reflector (PAR) lamps and transmissive bulbs for general lighting. Double-ended quartz capsules with coil legs
18
extending into the press or pinch
22
, as shown in
FIG. 1
, have passive extinction of electric arc at end-of-life. Elimination of non-passive failures in hard-glass halogen burners will enable marketing of thin-glass outer lamps containing the hard-glass burner.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a halogen incandescent capsule in hard-glass which passively extinguishes arcing which occurs at end-of-life, with a simple and economic construction.
According to the invention, this and other objects are achieved by a halogen incandescent capsule with a hard-glass envelope having at least one pinch seal at one end thereof and containing a filament, e.g. a tungsten filament. At least one leg of the filament extends into the pinch seal and is attached to a lead, e.g., a molybdenum lead, in the pinch seal.
When the filament fails at end-of-life, the arc is extinguished passively with disintegration of the filament leg in the cavity and near the inside surface of the pinch seal.
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 pinch is straight or has an increased pitch. The modified, e.g., stretched, coil leg reduces the extinction time and electric arc energy at the end-of-life due to reduced linear wire density near the pinch.
Modifying, e.g., stretching out, the coil leg enables a robust clamping of the tungsten wire in the molybdenum clamp with complete closure of the clamp. This eliminates clamping on the primary winding which requires a tight tolerance gap within the molybdenum clamp, which in turn, eliminates strain in the clamped leg and fractures of the coil leg. Clamping on the modified coil leg negates the requirement of changeover time between wattages at the mount machine.
For this reason, it is advantageous to modify both coil legs where they are clamped, whether or not the clamps are located in a press seal.
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Baker Karl
Fortuna Mary E.
Friederichs Winand H. A. M.
Vallabhaneni Eswara V.
Woods Joseph P.
Guharay Karabi
Halajian Dicran
Patel Nimeshkumar D.
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