Improved Means for Lighting by Electricity and Incandescence.
Year: 1896

page_text: Date of Application, 8th Dec., 1896
Comelade Inncifection Loft 9th Sont 1807
Accented 30th Oct
1807
PROVISIONAL SPECIFICATION.
Improved Means for Lighting by Electricity and Incandescence.
I, JOHN ARCHIBALD SINCLAIR, of 17, Elm Gardens, Hammersmith, in the County
of Middlesex, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to the production of light with the aid of bodies
rendered incandescent by means of an electric current, and permits of the employ-
ment, as an incandescing medium, of a substance which, at a given temperature,
radiates, as light, a greater proportion of the energy supplied than occurs, at the
same temperature, in the case of a carbon filament, such as commonly employeu
in an electric glow-lamp.
A lamp adapted for lighting by electricity and incandescence according to my
improved method consists of an exhausted bulb of the ordinary character in
which a loop or horse-shoe composed of carbon or other suitable electro-conductive
substance is mounted in the usual manner. This conductor is preferably flat in
cross section, the two sides of the loop being parallel. Arranged inside and out-
side the carbon loop and in close juxtaposition thereto are similar loops composed
of magnesium oxide or other substance of the character herein before referred to
and capable of being raised to a state of incandescence without suffering injury.
The carbon loop is slightly longer than the inner magnesium loop, and the
outer magnesium loop is slightly longer than the carbon loop; so that each loop
is free, under the influence of changes of temperature, to expand and contract
independently of the others. The three loops terminate in common bases to
which the leading-in wires are attached.
The passage of an electric current of adequate density through the carbon
conductor raises the latter to a state of incandescence, the heat thereof being
transmitted to the adjacent magnesia loops or strips; these being in turn heated
to incandescence and serving to emit light.
In preparing the magnesium oxide or other light emitting bodies; I prefer to
soak strips of paper, or other suitable organic substance of an absorbent character,
in a solution of the magnesium oxide or substance selected for use as a light-
emitting agent. A solution of magnesium sulphate may, for instance, be employed.
Having dried the strips, I wind them upon moulds adapted to impart the desired
horse-shoe or other form, and having wrapped the same in paper, I place them
in a crucible and expose them in a suitable furnace to a high temperature, access
of air being permitted. The paper is thus carbonised and burnt away, the
magnesium sulphate becomes decomposed and the substance of the strip converted
into magnesium oxide. The high temperature employed has the effect of rendering
the magnesia dense and specially suited for the purpose of the present invention.
Magnesium oxide strips prepared in the manner above described may if desired
he coated or impregnated with other substances adapted for lighting by incan-
descence. Such additional substances may be applied in the form of powder to
the surface of the strip; or the strip may be sprayed or otherwise moistened with
a solution of the additional substance, or with a liquid holding the said substance

page_text: in suspension. The strips may then be dried and fired in the manner usually
practised in the preparation of bodies intended for use in lighting by incan-
descence.
Dated this 2nd day of December 1896.
COMPLETE SPECIFICATION.
Improved Means for Lighting by Electricity and Incandescence.
I, JOHN ARCHIBALD SINCLAIR, of 17, Elm Gardens, Hammersmith, in the County
of Middlesex, Electrical Engineer, do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement:-.
This invention relates to the production of light with the aid of bodies
rendered incandescent by means of an electric current, and permits of the employ-
ment as an incandescing medium of a substance which, at a given temperature,
radiates, as light, a greater proportion of the energy supplied than occurs, at the
same temperature, in the case of a carbon filament, such as commonly employed
in electric glow-lamps.
A lamp adapted for lighting by electricity and incandescence according to my
improved method is illustrated in the accompanying drawings, whereof Fig. 1
is an elevation and Fig. 2 a side view of the body to be incandesced, and
consists of an exhausted bulb a of the ordinary character in which a loop or horse-
shoe composed of carbon or other suitable electro-conductive substance is
mounted in the usual manner. This conductor is preferably flat in cross section,
the two sides of the loop being parallel. Arranged inside and outside the carbon
loop band in close juxtaposition thereto, so as to reduce as much as "
possible the
exposed surface of the carbon, are similar but slightly wider loops cà, composed
of magnesium oxide or other substance of the character hereinbefore referred to
and capable of being raised to a state of incandescence without suffering injury.
The carbon loop is slightly longer than the inner magnesia loop c, and the
outer magnesia loop c is slightly longer than the carbon loop; so that each loop
is free, under the influences of changes of temperature to expand and contract
independently of the others. The three loops terminate in common bases to which
the leading-in wires d d are attached. In Figs. 3 and 4, I have shown an
alternative arrangement of loops or horseshoes; the carbon conductor being in
the form of a flat horseshoe b, while the light-emitting body. c*, which is composed
of a strip, preferably of a width slightly exceeding the transverse dimension of
the carbon horseshoe b is arranged outside the carbon conductor in such a manner
that only the edges of the latter are visible.
The passage of an electric current of adequate density through the carbon
conductor raises the latter to a state of incandescence, the heat thereof being
transmitted to the adjacent magnesia loops or strips; these being in turn heated
to incandescence and emitting light.
In cases where the strip or loop is composed of an electro-conductive substance, it
should be arranged out of contact with the filament or conductor.
It may also be remarked that, for a given candle power, the strip or loop
should possess a larger radiating surface than that required with a carbon filament
as ordinarily constructed by reason of its lower emissivity; but it must be borne
in mind that, for the same reason, proportionately less power will be required to
maintain the said strip or loop at a given temperature.

page_text: In preparing the magnesium oxide or other light-emitting bodies, I prefer to
soak strips of paper, or other suitable organic substance of an absorbent character,
in a solution of magnesium oxide or other substance selected for use as a light-
emitting agent. A solution of magnesium sulphate may, for instance, be employed.
Having dried the strips, I wind them upon moulds adapted to impart the desired
horseshoe or other form whilst permitting shrinkage to take place; and having
wrapped the same in paper, I place them in a crucible and expose them in a
suitable furnace to an extremely high temperature, access of air in a very limited
degree being permitted. The paper is thus carbonised and burnt away, without
the production of flame, which would tend to distort the horseshoe at this stage;
the magnesium sulphate becomes decomposed, and the substance of the strip
converted into magnesium, oxide. If found desirable, these magnesium oxide
horseshoes may be soaked in Epsom salts and again fired. The high temperature
employed has the effect of rendering the magnesia dense, and specially suited for
the purpose of the present invention.
When the substance used for radiating is of an expensive nature, it may be
applied in the form of powder to the surface of the strip; or the strip may be
sprayed or otherwise moistened with a solution of the additional substance, or with
a liquid holding the said substance in suspension. The strips may then be dried
and fired in the manner usually practiced in the preparation of bodies intended
for use in lighting by incandescence.
If the light-emitting horseshoes be prepared from substances other than
magnesia, but which would be liable to injury on coming into contact with the
carbon filament, the surfaces of the horseshoes in juxtaposition to the filament
may be coated with magnesia or like substance incapable of being so affected.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim:-
1. For use in the production of light by electricity and incandescence, a light-
emitting medium composed of magnesium oxide, or of other like oxide, whereof
the surface is heated by contact with or by radiation from a carbon or other
electro-conductive body, the light-emitting and the heating media being capable
of independent expansion or contraction.
2. The herein described process for preparing media for use in the production
of light by electricity and incandescence, consisting in soaking strips of an organic
nature, such as paper, in a solution of magnesium sulphate, or other like substance,
drying the strips so treated, winding the same upon suitable moulds and wrapping
them in paper; then exposing them to a high temperature in a suitable furnace
to which access of air to a very limited extent is permitted, whereby the paper
is consumed, the magnesium sulphate is decomposed and the substance of the
strip becomes converted into magnesium oxide.
3. In a lamp for lighting by electricity and incandescence, the employment
of a light-emitting medium prepared substantially as herein described and
arranged in conjunction with a conductor of carbon or other suitable electro-
conductive substance so as to be heated thereby, substantially as set forth.
4. For use in lighting by electricity and incandescence, a lamp constructed or
operating substantially as herein described. with reference to Figs. 1 and 2 or to
Figs. 3 and 4 of the accompanying drawings.
C
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.