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Патент USA US2106689

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Jan. 25, 1938.
_ Filed Aug. 25 , 1932
Patented Jan. 25, 1938
Chester H. Braselton, New York, N. Y., assignor
to Sirian Lamp Company, Newark, N. J., a cor
poration of Delaware
Application August 25, 1932, Serial No. 630,380
2 Claims.
This invention relates to incandescent elec
tric lamps and particularly-to a light emitting
?lament therefor.
Where a tantalum ?lament is used in an elec
5 tric lamp it has the tendency to absorb gases
from the interior of the bulb at comparatively
low temperatures. The effect of the absorption
of gases on the tantalum raises its resistance,
and therefore less current will flow through the
wire and the wire will not be raised to as high a
temperature as originally intended. Thus the
longer a tantalum lamp is burned the more
gases are absorbed by the ?lament, and they re
sistance gradually increases and the light emis
sion from the ?lament becomes lower and lower.
The rate of absorption, however, is much lower
when the tantalum is maintained at relatively
high temperatures, and. it is therefore one of the
objects of the present invention to maintain a
20 tantalum ?lament at a high temperature re
gardless of its absorption of gases so that the
rate of absorption will be relatively low and the
light emission will be maintained at a constant
high ?gure.
Another object of the invention is to increase
the mechanical strength of a lamp ?lament at
high temperatures.
Other objects of the invention will be ap
parent as the description thereof proceeds.
One embodiment of the invention has been
illustrated in the accompanying drawing in
Fig. l is a side elevational view of anelectric
lamp embodying the particular type of ?lament;
35 and
Fig. 2 is an enlarged view partly in section of
the ?lament used.
In Fig. 1 of the drawing an incandescent elec
tric lamp is shown having the usual form with
40 an envelope ID of glass or other suitable trans
parent material provided with an inturned press
H which has fused to it at approximately the
center thereof an upstanding glass‘rod l2 which
(Cl. 176-40)
plurality of wires twisted together, one of the
wires being tantalum and the other being a wire
having a higher melting point than tantalum.
For purposes of illustration I have shown in Fig.
2 a tantalum wire l9 twisted together with a 5
tungsten wire 20 and the twisted ?lament thus _
formed wound in a concentrated coil illustrated
by the turns 2| at the right hand side of the ?g
When current is run through the ?lament 10
the temperature of the entire ?lament is main
tained slightly higher than the temperature
would be if the ?lament were made of tantalum
only, and thus the tantalum in the ?lament is
prevented from absorbing gases and its resist- 15
ance is maintained at a constant ?gure. If,
however, the tantalum does absorb some gases
and thereby attains a higher resistance, more
current will ?ow through the tungsten wire with
the result that its temperature will be raised 20
slightly and the temperature of the tantalum will
thereby be increased due to its physical contact
with tungsten. The ?lament of the invention,
therefore, has the advantages of a tantalum ?la
ment with the disadvantages thereof largely 25 ,
While a single wire each of tantalum and
tungsten may be found preferable the invention
also contemplates the use of a larger number of
wires either twisted together or braided,‘ and 30
these wires may be equally divided between tan
talum and tungsten or there may be one tung
sten wire with several tantalum wires or, vice
versa. The tightness of the coiling or braiding
may also be varied considerably as a loosely 35
wound coil or braid may be made to accomplish
the desired result, it being only necessary to have
the tantalum within the high temperature zone
of the tungsten to maintain the temperature of
the tantalum at a point slightly higher than its 40
normal temperature for the current consumed.
Other modi?cations of the invention may be
resorted to without departing from the spirit
45 part of the bulb and terminates in a button l3. - thereof and I do not, therefore, desire to limit
A pair of support rods M are sealed in the press myself to what has been shown and described 45
extends upwardly to a point adjacent the largest
II and have lead-in wires l5v connected to the
lower ends thereof. The lighting ?lament I6 is
attached to the upper ends of the support rods
50 l4 and extends in a circular curve around the
button I3, there being a plurality of support
wires l'l sealed in the button l3 and provided
with pig-tails I 8 at their ends to support the
?lament in its proper position.
The ?lament itself is preferably formed of a
except as such limitations occur in the appended
What I claim is:
1. An incandescent electric lamp comprising a
globe having electric circuit leads, a ?lament of 50
tantalum electrically connected at opposite ends
directly with said leads, and means for heating
said tantalum ?lament to temperatures in ex
cess of its normal lighting temperature com"
prising a tungsten ?lament electrically connect- 55
ed at its opposite ends with said leads in com
plete electrical parallelism with said tantalum
?lament and in contact therewith throughout its
length, the cross-section of the tantalum and
tungsten ?laments being substantially equal.
2. An incandescent electric lamp comprising a
globe having electric circuit leads, a ?lament of
tantalum electrically connected at opposite ends '
directly with said leads, and means for heating
said tantalum ?lament to temperatures in excess
of its normal lighting temperature comprising a
tungsten ?lament electrically connected at its
opposite ends with said leads in complete elec
trical parallelism with said tantalum ?lament
and in contact therewith throughout its length.
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