IMPROVEMENTS IN THE MANU- FACTURE OF INCANDESCENT ELECTRIC LAMPS
Year: 1882

page_text: LETTERS PATENT to St. George Lane Fox, of Queen Anne's Gate in the
City of Westminster for an invention of "IMPROVEMENTS IN THE MANU-
FACTURE OF INCANDESCENT ELECTRIC LAMPS"
PROVISIONAL SPECIFICATION left by the said St. George Lane Fox at the
Office of the Commissioners of Patents on the 5th April 1882.
ST. GEORGE LANE Fox of Queen Anne's Gate in the City of Westminster,
"IMPROVEMENTS IN THE MANUFACTURE OF INCANDESCENT ELECTRIC LAMPS"
My Invention consists of improvements in the manufacture of incandescent
electric lamps and it relates to the thickening of the ends of the carbon filaments
in order to reduce the resistance at those parts and thus prevent excessive heating
of the platinum or other conductors to which the carbon filaments are connected―
In the Specifications of former Letters Patent granted to me and dated respec-
tively 28th August 1880 No 3494 and 18th January 1881 No 225, I have
explained certain methods of thickening the ends of the filament by causing carbon
to be deposited upon them while immersed in a medium of coal gas or carbon
compound, and raising the ends to the necessary heat by a current of electricity..
The object of my present Invention is to carry out this method in a more
practical and economical manner and the Invention consists in producing the
necessary heat to cause the deposit of carbon by forming an electric arc.
I insert the ends of the filament into holders on the ends of the platinum wires
and these holders may conveniently be in the form of spirals such as described in
the Specification of my said Letters Patent of 18th January 1881, and in order to
cause the parts to adhere together I may use a cement formed of Chinese ink and
plumbago or other suitable ingredients. I then make one of the connections
between the platinum and the filament, one of the poles of a circuit the other pole
of which consists of a piece or block of carbon or plumbago. I immerse the whole
in a medium of coal gas or hydro carbou compound and send a current through the
circuit I then cause the end of the carbon block to touch the platinum or the

page_text: filament at or near the point of connection and then immediately withdraw it,
the effect being that an electric arc is formed which produces heat and causes
carbon to be deposited, partly from the gas and partly from the carbon block, upon
the platinum or filament at the point of contact. I vary the point of contact of
the carbon block from time to time so as to obtain a sufficient layer of carbon
upon the platinum holder and also upon the part of the filament next the holder.
I consider it best to thicken the filament by means of this deposit for a distance of
say th of an inch from the holder and it is desirable that this increased thickness
should taper from the holder. When the deposit of carbon at one of the connections
of the filament with the corresponding holder has thus been formed I treat the
connection with the other holder in the same manner.
In order to favour the deposit of the carbon upon the platinum holder I may
coat the latter with a cement such as that herein before mentioned.
-
"

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said St. George Lane Fox in the Great Seal Patent Office on the
5th October 1882.
ST. GEORGE LANE Fox of Queen Anne's Gate in the City of Westminster
"IMPROVEMENTS IN THE MANUFACTURE OF INCANDESCENT ELECTRIC LAMPS
35
My Invention consists of improvements in the manufacture of incandescent
electric lamps and it relates to the thickening of the ends of the carbon filaments
in order to reduce the resistance at those parts and thus prevent excessive heating
of the platinum or other conductors to which the carbon filaments are connected.
In the Specifications of former Letters Patent granted to me and dated respec-
tively 28th August 1880 No 3494 and 18th January 1881 No 225 I have
explained certain methods of thickening the ends of the filament by causing carbon
to be deposited upon them while immersed in a medium of coal gas or carbon
compound, and raising the ends to the necessary heat by a current of electricity.
The object of my present Invention is to carry out this method in a more
practical and economical manner and the invention consists in producing the
necessary heat to cause the deposit of carbon by forming an electric arc. I insert
the ends of the filament into holders on the ends of the platinum wires and these
holders may conveniently be in the form of spirals such as described in the Speci-
fication of my said Letters Patent of 18th January 1881, and in order to cause the
parts to adhere together, I may use a cement formed of Chinese ink and plumbago
or other suitable ingredients. I then make one of the connections between the
platinum and the filament one of the poles of a circuit, the other pole of which
consists of a pencil or block of carbon or plumbago. I immerse the whole in a
medium of coal gas or carbon compound-I then cause the end of the carbon block
to touch the platinum or, the filament at or near the point of connection and then
immediately withdraw it the effect being that an electric arc is formed which
produces heat and causes carbon to be deposited, partly, from the gas and partly
from the carbon block upon the platinum or filament at the point of contact-I
vary the point of contact of the carbon block from time to time so as to obtain a
sufficient layer of carbon upon the platinum holder and also upon the part of the
filament next the holder-I consider it best to thicken the filament by means of
this deposit for a distance of say th of an inch from the holder and it is desirable
that this increased thickness should taper from the holder. When the deposit of
carbon at one of the connections of the filament with the corresponding holder has
thus been formed I treat the connection with the other holder in the same
manner.
In order to favor the deposit of the carbon upon the platinum holder I may coat
the latter with a cement such as that hereinbefore mentioned.
The accompanying drawings illustrate my Invention, Figure 1 being a front
elevation, Figure 2 a side elevation, and Figure 3 a plan. a a is a carbon filament
with its ends inserted into spirals bb on the ends of the platinum wires cc;
these wires are attached to the stopper d of a bottle or vesself which is supplied
with coal gas or other carbon compound, g being the gas inlet and the gas outlet.
2. is a spring in contact with both the platinum wires c'c so that the connection of
either of them with the filament a can form one of the poles of a circuit. 1 are
two pieces of carbon or plumbago either of which can be made the other pole of
the circuit as required. The pieces of carbon 77 pass through openings in the sides
of the bottle and these openings are provided with india rubber m fitting round
the carbons so as to prevent escape of gas. It is preferred to mount the carbons in
metal holders n n Figure 1 having metal clips oo so that by connecting the

page_text: wires pp to the holders outside the bottle the current passes along the holders to
the clips o o and to the carbons inside the bottle; as the carbons become consumed
they can be pushed further through their holders. The mode of forming the electric
arc so as to cause the deposit of carbon on the ends of the filament a has been
already herein explained.
Having now described the nature of my said Invention and in what manner the
same is to be performed I declare that I claim :—
Producing by means of an electric arc substantially as described the necessary
heat to cause a deposit of carbon upon the ends of carbon filaments for incandescent
electric lamps when immersed in a medium of coal gas or other carbon compound
for the purpose explained.
In witness whereof I the said St. George Lane Fox have hereunto set my hand
and seal this fifth day of October One thousand eight hundred and eighty
two
ST. G. LANE FOX. (L.S.)