Improvements in Electric Incandescent Lamps
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Incandescent Lamps.
A communication from JOHN WARING, of Manchester, in the County of Hartford
State of Connecticut, U.S.A., Manufacturer.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
Chartered Patent Agent do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
The invention relates to the class of lamps which have an enclosed conductor
adapted to be raised to incandescence by electrical excitation, the object being to
provide a lamp which will more perfectly maintain a uniform candle power
throughout its life, than prior lamps of this class.
It has been taught by high authorities, and generally accepted by those familiar
with the art, that if the carbon of an incandescent lamp is not placed in a vacuum,
even though it is surrounded by a gas which does not chemically attack the carbon,
the "air washing" or rapid passage of the molecules of gas over the highly heated
surface of the carbon will produce a disintegration of the carbon. It has also been
well known that if an incandescent carbon is surrounded by an atmosphere of
hydrogen or nitrogen, the rapidly moving molecules of gas will carry off the heat
from the carbon and thus require the expenditure of much more energy to keep the
carbon at the desired state of incandescence. It has been accordingly supposed
that it was absolutely necessary to place the carbon in a nearly perfect vacuum,
that is to say, in a sealed chamber having an interior gas pressure of only about
one millionth of an atmosphere, in order to avoid the above difficulties and render
the carbon stable.
My correspondent has discovered that if a carbon in a sealed chamber is
surrounded by a gas of great specific density that is to say, a gas most of whose
elements have a high atomic weight, the dissipation of energy by loss of heat from
the carbon is reduced, so that as a factor it may be ignored; also that, by using as
a surrounding medium a gas which has no injurious chemical effects on the carbon,
the disintegration of the carbon caused by high temperature is probably lessened as
the blackening of the glass of the lamp is materially lessened and the stability
of the carbon is proportionately increased, and a lamp is produced which is efficient
at the commencement of its life, and which will maintain its efficiency much longer
than a lamp having its carbon in a vacuum. My correspondent shows that these
advantages above described are obtained by enveloping the carbon with a gas con-
sisting of the vapour of bromine, or of the vapour of iodine, or of a mixture of both,
the atomic weight of these elements being high.
Such a lamp may be made as illustrated in the accompanying drawings, where
1 indicates the lamp with a common carbon and connection; 2 an ordinary tubular
fork to which the lamps may be connected in the usual manner; 3 a tube provided
with suitable controlling cocks 4 and 5, leading to a reservoir 6 containing the gas
of great mean molecular weight with which the carbon is to be enveloped; and 7 a
tube leading to an air pump. The globes may be filled with the gas by partially
withdrawing the atmospheric air by means of the pump, and then opening the
cocks controlling the passage from the gas reservoir. The gas may be generated
by heat or otherwise, bromine, for instance vaporizing easily, but iodine requiring
heat.
This gas admitted to the globes and diluted by the air remaining in them is then
partially withdrawn and more gas allowed to enter, this process being repeated
until the extent to which the desired gas is diluted with foreign gases has become

page_text: practically infinitesimal. If preferred, the atmospheric air may be at first exhausted
as nearly as possible, and the desired gas then admitted around the carbon.
The amount of gas to be admitted will in practice vary with the size of the
enclosing chamber, with the nature of the gas, and probably also, with the nature
of the other elements of the lamp. In either of the above processes it is easy to
regulate, in a lamp of given construction, the amount of gas admitted, so as to give
the best results.
Having now particularly described and ascertained the nature of the said inven-
tion, as communicated to me by my foreign correspondent, and in what manner
the same is to be performed, I declare that what I claim is ;-
1. The combination of a carbon to be raised to incandescence by electrical
excitement an enveloping gas composed wholly or largely of an element or elements
of high atomic weight, to wit as high as that of bromine a sealed chamber enclosing
both the carbon and surrounding gas and electrical conductors passing through the
walls of said chamber and connecting with the carbon for the purpose specified.
2. The combination of a carbon to be raised to incandescence by electrical excite-
ment an enveloping gas consisting wholly or largely of bromine or of iodine or of
both a sealed chamber enclosing both the carbon and surrounding gas and electrical
conductors passing through the walls of said chamber and connecting with the
carbon for the purpose specified.
Dated this 9th day of May 1893.
W. P. THOMPSON & BOULT,
Agents for the Applicant.