IMPROVEMENTS IN ELECTRIC LAMPS
Year: 1881

page_text: LETTERS PATENT to St. George Lane Fox, of 4, Grosvenor Gardens, in the
County of Middlesex, for an Invention of "IMPROVEMENTS IN ELECTRIC
LAMPS."
PROVISIONAL SPECIFICATION left by the said St. George Lane Fox at the
Office of the Commissioners of Patents on the 8th April 1881.
ST. GEORGE LANE Fox, of 4, Grosvenor Gardens, in the County of Middlesex.
"IMPROVEMENTS IN ELECTRIC LAMPS."
My Invention has reference to those electric lamps in which the light is produced
by the incandescence of a continuous conductor or luminous bridge.
In my improved lamp the platinum wires which form the connection between
the copper conducting wires or terminals and the luminous bridge are fused at their
upper part into English lead glass, and their upper ends extend into tubes con-
taining mercury, into which the conducting wires dip, all as described in a
Provisional Specification lodged by me on the 18th January, 1881, No. 225. I
force over the lower end of each of the platinum wires a cylinder or block of carbon
or plumbago, which has a small hole drilled through its centre for the purpose. I
cement the platinum wires in these cylinders or blocks with Indian ink, and in
order to give the cement a better hold, the wires may be roughened by having a
screw thread formed thereon or otherwise. Into the lower ends of the cylinders or
blocks I push the ends of the carbon filament forming the luminous bridge, so that
the ends of the filament and of the platinum wires may meet, and I also cement
the ends of the filament into the cylinders or blocks. Sometimes instead of Indian
ink I use a cement composed of Indian ink and finely divided plumbago. The
platinum wires project only about th's of an inch below the lead glass into which
they are fused, and their whole length is only about th's of an inch.
In order to avoid the liability of air remaining in the bottom of the mercury
tubes when they are filled with mercury, and gradually finding its way into the
lamp flask, thereby destroying the vacuum therein, I make the lower parts of the
tubes with an enlargement or approximately of spherical or bulb shape, so that as
the mercury is poured in the air may have room to escape.
I fill the tubes above the mercury with marine glue or other suitable cement.
Over this I place plaster of Paris, and I cover the top of the neck of the flask
with a cap of wood or other suitable material cemented to the glass with plaster of
Paris.
In some cases I substitute for the platinum wires in electric lamps cylindrical
pieces or sticks of plumbago, which I secure to the glass by carefully "melting in."

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
8th October 1881.
ST. GEORGE LANE Fox, of 4, Grosvenor Gardens, in the County of Middlesex.
IMPROVEMENTS IN ELECTRIC LAMPS."
My Invention has reference to those electric lamps in which the light is produced
by the incandescence of a continuous conductor or electric bridge.
In my improved lamp the platinum wires which form the connection between
the copper conducting wires or terminals and the electric bridge are fused at their
upper part into English lead glass, and their upper ends extend into tubes con-
taining mercury, into which the conducting wires dip, all as described in the
Specification of former Letters Patent granted to me, and dated 18th January,
1881, No. 225. I force over the lower end of each of the platinum wires a
cylinder or block of carbon or plumbago, which has a small hole drilled through
its centre for the purpose. I cement the platinum wires in these cylinders or
blocks with (genuine) Indian or Chinese ink, and in order to give the cement a
better hold, the wires may be roughened by having a screw thread formed thereon
or otherwise. Into the lower ends of the cylinders or blocks I push the ends of
the carbon filament forming the electric bridge, so that the ends of the filament
and of the platinum wires may meet, but it is not necessary they should meet, and
I also cement the ends of the filament into the cylinders or blocks. Sometimes
instead of Indian or Chinese ink I use a cement composed of Indian or Chinese
ink and finely divided plumbago.
By my improved method of connecting the bridge to the platinum wires the
latter need project only about th's of an inch below the lead glass into which
they are fused, and their whole length need be only about th's of an inch.
In order to avoid the liability of air remaining in the bottom of the mercury
tubes when they are filled with mercury, and gradually finding its way into the
lamp flask, thereby destroying the vacuum therein, I make the lower parts of the
tubes with an enlargement or approximately of spherical or bulb shape, so that as
the mercury is poured in the air may have room to escape.
I fill the tubes above the mercury with cotton wool, and over this I place plaster
of Paris.
The accompanying Drawing represents a vertical section of a lamp made according
to my present Invention. a, a, is the flask or globe; b, b, are the mercury tubes
formed with spherical enlargements or bulbs 61, 61, at their lower ends for the
purpose already explained; & is the cotton wool above the mercury in the tubes b,
and e is the plaster of Paris over the cotton wool; f, f, are the conducting wires or
terminals; g, g, are the platinum wires fused into the bottoms n, n, of the tubes b,
and extending up into the mercury in these tubes; h, h, are the cylinders or blocks
of plumbago or carbon with holes drilled in their upper ends so as to allow of their
being forced over the lower ends of the wires g, as shown, the wires being cemented
in the cylinders by Indian or Chinese ink; i is the electric bridge, the ends of
which are inserted into holes or slits in the lower ends of the cylinders h, h, and
they are similarly cemented with Indian or Chinese ink. The ink is applied
to the ends of the bridge i, and dabbed round the holes in the cylinders, as seen
at k, k.
Having now described the nature of my said Invention, and in what manner the
same is to be performed, I declare that I claim,―
First. Connecting the platinum wires and the bridge of electric lamps by means
of cylinders or blocks of carbon or plumbago, into which the ends of the said wires

page_text: and the ends of the bridge are inserted, and in which they are cemented,
substantially as hereinbefore described.
Second. Making the mercury tubes with bulbs or enlargements at their lower
ends, substantially as and for the purpose hereinbefore described.
In witness whereof, I, the said St. George Lane Fox, have hereunto set my
hand and seal, this Sixth day of October, One thousand eight hundred and
eighty one.
ST. G. LANE FOX. (L.S.)