Improved Means for Lighting by Electricity and Incandescence.
Year: 1897

page_text: 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 electro-
conductive or non-conductive bodies rendered incandescent by means of an electric
current, and permits of the employment, 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 one
method of construction 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 may be flat in cross
section, the two sides of the loop being parallel. Arranged inside and outside 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 magnesia loop, and the outer magnesia
loop 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
are attached.
The passage of an electric current of adequate density through the carbon con-
ductor raises the latter to a state of incandescence, the heat thereof being trans-
mitted 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 substance of an absorbent character, in a
solution of or containing 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 horseshoe or other form; and having wrapped the same in paper, I
place them in a crucible and heat them slowly 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 pure and specially suited for the
purpose of the present invention.

page_text: According to another method of preparing the light-emitting bodies, I spread
a sheet of paper or other suitable substance in a vessel, and pour upon it, to a known
depth, a liquid, which may be water, into which is stirred a known weight of
magnesia or other selected light-emitting agent in the form of a fine powder. Or
allowing a settlement to take place, a film of magnesia of known thickness is
obtained on the paper; the supernatant liquid being then carefully removed with
the aid of a syphon or otherwise. The paper and film having been dried are sub-
jected to treatment for imparting the required form and then exposed to heat as
before described. In some cases I may flood the paper film before drying with
gum-water or other fixing solution so as to secure the film to the paper. When
dried a film so treated is not liable to become disintegrated by handling.
Magnesium oxide strips or bodies prepared in the manner above described may,
if desired, be coated or impregnated with other substances adapted for lighting
by incandescence. Such additional substances may be applied to the surface
remote from, or out of contact with, the carbon in the form of powder; or the strip
may be sprayed or otherwise moistened with a solution of or containing 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 practised in the
preparation of bodies intended for use in lighting by incandescence.
According to an alternative method, the filament is made in the form of a tube
with a closed end and having two longitudinal slots arranged diametrically opposite
each other. This film or filament is preferably composed of carbon, and may be
produced from cellulose, or other suitable material, moulded to the required shape,
mounted upon a form, and gradually raised to a high temperature in the absence
of air, as in the case of filaments for ordinary glow-lamps. In some cases, I may
use paper or other material which does not admit of being moulded; the tube
being then formed from two separate strips of paper, each bent to a semi-circular
form and joined together by means of another strip of the material from which the
filament is formed wound once round the end and secured with the aid of a car-
bonisable cement. The envelope or light-emitting body has the same shape at
the end as the round-ended filament, is not slotted, is rather longer and larger than
the filament, and is made of the desired oxide, according to either of the methods
herein described. The envelope may be strengthened by longitudinal ribs. Small
discs of the oxide used, of the same diameter as the filament, are prepared by
treating discs of paper in the manner above described.
For convenience in handling, I prefer to bend the ends of the leading-in wires
into a semi-circle, the plane of which is at right-angles to the wire, and to join
them by means of a small piece of glass.
In arranging the filament and envelope, I take a pair of leading-in wires and fix
them, for convenience, in a holder with their semi-circles in the same horizontal
plane and in coincidence with the diameter of the tube. Having moistened two
of the semi-circular strips with a suitable cement, such as thickened Indian ink,
I place one of the small discs of oxide upon the wires so that it lies concentrically
therewith. Above this, with each of its lower limbs touching one of the wires only,
is deposited the film, and, having made the joint good with cement, the magnesia
envelope or light-emitting body is placed over it; the body being joined to the
wires by cementing. The incandescing body is then set aside. to dry, and is sub-
sequently sealed into a bulb. Exhaustion may be performed in the usual manner.
A pin-hole should have been formed in the disc of oxide to permit of the escape
of air from within the envelope during exhaustion.
Where the film and envelope are too thin to support themselves, I make an oxide
cylinder by the methods already described, and of sufficient thickness to afford
the requisite strength. This is cemented to the wires, and over it is slipped the
film, which is also connected with the wires, both physically and electrically. Over
this again is, slipped the thin oxide envelope, which is joined to the wires. Accord-
ing to this mode of construction, the upper and lower end-pieces may be dispensed

page_text: with if the cylinder, the film, and the envelope fit together, so that only a neglige
able portion of the film is exposed and able to radiate directly to the bulb.
In some instances; the substance of the envelope may be of such a character as
to be harmfully acted upon when in contact with the incandescent film or filament,
as also to require support. Or the substance of the envelope may be electro-
conductive and therefore liable to short-circuit the filament. In either of these
cases, a thin magnesia rod is passed axially through the film or filament and cap,
the latter being perforated for its passage. The rod is held at the lower end by
a wire sealed into the bar of glass which joins the leading-in wires. The envelope
is sufficiently large in diameter to maintain a free space between it and the filament
and is cemented to the magnesia rod at the top and to a magnesia cap or disc at the
bottom; the magnesia cap or disc being also fixed to the magnesia rod. The
cement used should consist mainly of a suitable oxide.
In constructing lamps which produce light by means of electricity and incan-
descence, as herein described, it is necessary, in order to obtain the longest life at
a given efficiency, that the filament be so proportioned with regard to the envelope
or light-emitting body that the temperature of the former may be as little as
possible in excess of the latter. That the film or filament be almost or completely
surrounded by the envelope. That the film and envelope should both have a
uniform temperature; the latter being as thin as is consistent with the mechanical
strength required, and possessing as high a thermal conductivity as possible. That
the envelope should, at a given temperature, radiate as much light and as little
heat as possible; and that loss of heat by conduction along the leading-in wires
and by convection due to inferior exhaustion should be reduced to a minimum.
*1 100%
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 electro-
conductive or non-conductive bodies rendered incandescent by means of an electric
current as described in the Specification to Letters Patent granted to me and dated
8th December, 1896, No. 28,101, and permits of the employment, 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.
In the accompanying drawings, Fig. 1 represents in side elevation a filament
constructed according to my invention; Fig. 2 being a similar view of the light-
emitting envelope or body.. Fig. 3 is an elevation of an alternative construction
of filament. Fig. 4 is a perspective view of the leading-in wires employed in con-
nection with the improved incandescing bodies. Fig. 5 is an elevation of the
filament and light-emitting body mounted on the leading in wires. Fig. 6 is a
vertical section of another mode of constructing the incandescing body; Fig. 7
shewing a further alternative construction.

page_text: A lamp adapted for lighting by electricity and incandescence according to my
improved méthod consists of an exhausted bulb of the ordinary character in which
a conductor composed of carbon or other suitable electro-conductive substance,
having in close juxtaposition thereto a body composed of magnesium oxide or other
substance possessing the characteristics herein before referred to and capable of
being raised to a state of incandescence without suffering injury. 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 body which in turn becomes heated to incandescence and emits light.
The light-emitting body or hood A is prepared according to the method described
in my said previous specification.
Referring to Fig. 1 of the accompanying drawings, the filament is made in the
form of a tube a with or without a closed end and having two longitudinal slots b
arranged diametrically opposite each other. Or any other convenient number
of narrow slots may be made in the filament so that the current passing up and
down the tube may enter and leave it at the same end, and thereby encounter
the desired resistance. This film or filament is preferably composed of carbon,
and may be produced from cellulose or other suitable material moulded to the
required shape, mounted upon a form, and gradually raised to a high temperature
in the absence of air, as in the case of filaments for ordinary glow-lamps. The
light-emitting body to be used with this filament may be in the form of a hood
as shown in Fig. 2.
Referring to Fig. 3, when using paper or other material which does not admit
of being moulded, the tube may be formed from two separate strips of paper a*a*
each bent to a semi-circular form and joined together by means of another strip c
of the material from which the filament is formed wound once round the end and
secured with the aid of a carbonisable cement.
The hood or light-emitting body has the same shape at the upper end as the
filament illustrated in Fig. 1, is not slotted, is rather longer and larger than the
filament, and is made of the desired oxide, according to the method described in
my said former specification. The envelope may be strengthened by longitudinal
ribs. Small discs of the oxide used, of the same diameter as the filament, are
prepared by treating discs of paper in the manner above referred to.
For convenience in handling I prefer to join the leading-in wires e e by means
of a small piece of glass e², the ends of the wires being bent into a semi-circle el
as shewn in Fig. 4. The object in forming the wires with semi-circular portions
for effecting the attachment to the filament is to ensure an equal distribution of
current. In arranging the filament and envelope, I take a pair of leading-
wires e e and fix them, for convenience, in a holder with their semi-circles e¹ e¹ in-
the same horizontal plane and in coincidence with the diameter of the tube.
Having moistened the semi-circular portions of the wires with a suitable cement,
such as thickened Indian ink, I place one of the small discs f of oxide upon the
wires so that it lies concentrically therewith as shewn in Fig. 5. Above this with
each of its ends touching one of the wires only is deposited the film a or a³, and
having made the joint good with cement, the magnesia envelope or light-emitting
body A is placed over it; the body being joined to the wires by cementing the same
thereto. The incandescing body is then set aside to dry, and is subsequently
sealed into a bulb. Exhaustion may be performed in the usual manner, except
that the vacuum must be very high. Should, for example, hydrogen, which
possesses very great convective power, be found the remanent gas and a perceptible
loss of heat occur, the bulb may be washed out by admitting a little air and
re-exhausted. A pin hole should have been formed in the disc of oxide to permit
of the escape of air from within the envelope during exhaustion.
Where the film and envelope are too thin to support themselves, I construct the
incandescing body as shewn in Fig. 6. I make an oxide cylinder A° by the method
herein referred to, and of sufficient thickness to afford the requisite strength. This

page_text: is cemented to the wires e, e, and over it is slipped the film a, which is also con-
nected with the wires both physically and electrically. Over this again is slipped
the thin oxide envelope A, which is joined to the wires. According to this mode
of construction, the upper and lower end-pieces may be dispensed with if the
cylinder, the film, and the envelope fit together so that only a negligeable portion
of the film is exposed and able to radiate directly to the bulb. The light-emitting
body must not, however, be so thin as to allow the passage of light or of heat.
In some instances, the substance of the envelope may be of such a character as
to be harmfully acted upon when in contact with the incandescent film or filament,
as also to require support.. Or the substance of the envelope may be liable to short
circuit the filament. In either of these cases, the film a is supported and main-
tained in position out of direct contact with the envelope A by means of a thin
magnesia rod g (Fig. 7) which is passed axially through the film or filament, the
latter being perforated at the upper end if necessary for its passage. The rod is
held at the lower end by a wire h, sealed into the bar of glass e2 which joins the
leading-in wires e e. The envelope A is sufficiently large in diameter to maintain
a free space between it and the filament a and is cemented to the magnesia rod
at the top and to a magnesia cap or disc f at the bottom; the magnesia cap or disc
being also fixed to the magnesia rod. The cement used should consist mainly of a
suitable oxide.
In constructing lamps which produce light by means of electricity and incan-
descence, as herein described, it is necessary, in order to obtain the longest life at
a given efficiency, that the filament be so proportioned with regard to the envelope
or light-emitting body that the temperature of the former may be as little as possible
in excess of the latter. That the film or filament be almost or completely sur-
rounded by the envelope; both the film and envelope when viewed in the same
direction exhibiting as nearly as possible the same amount of surface. That the
film and envelope should both have a uniform temperature; the latter being as
thin as is consistent with opacity for light and heat and the mechanical strength
required, and possessing as high 'a thermal conductivity as possible. That the
envelope should, at a given temperature, radiate as much light and as little heat
as possible; and that loss of heat by conduction along the leading-in wires and by
convection due to inferior exhaustion should be reduced to a minimum.
Having now particularly described and ascertained the nature of my said
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 body composed of a tube or hood of magnesium oxide, or other like oxide,
arranged in juxtaposition and as an envelope to a carbon filament in the form of
a slotted tube; the envelope and the carbon filament being severally joined to the
leading-in wires, substantially as set forth.
2. The improved filament for use in the production of light by electricity and
incandescence, constructed or arranged substantially as described with reference
to Fig. 1 or to Fig. 3 of the accompanying drawings.
3. For use in the production of light by electricity and incandescence, a light-
emitting body constructed or operating substantially as described with reference
to Fig. 5 of the accompanying drawings.
4. For use in the production of light by electricity and incandescence, a light-
emitting body constructed or operating substantially as described with reference
to Fig. 6 of the accompanying drawings.
5. For use in the production of light by electricity and incandescence, a light-
emitting body constructed or operating substantially as described with reference.
to Fig. 7 of the accompanying drawings.
6. In mounting light-emitting bodies of the character herein referred to, the
employment of leading-in wires having their extremities bent so as to assume a
semi-circular form, substantially as and for the purpose set forth.
7. In fitting leading-in wires to light-emitting bodies of the character herein

page_text: referred to, the employment substantially as herein described of oxide discs or caps
to which the leading-in wires are cemented.
Dated this 14th day of February 1898.
..
referred to, the employment substantially as herein described of oxide discs or caps
to which the leading-in wires are cemented.
Dated this 14th day of February 1898.
.
G. G. M. HARDINGHAM,
Chartered Patent Agent, 191, Fleet Street, London, E.C.
G. G. M. HARDINGHAM,
Chartered Patent Agent, 191, Fleet Street, London, E.C.