IMPROVEMENTS IN CARBONS FOR ELECTRIC LAMPS.”
Year: 1882

page_text: LETTERS PATENT to Arthur Smith of Rookwood House Wickham Road
Brockley in the County of Kent for an invention of "IMPROVEMENTS IN
CARBONS FOR ELECTRIC LAMPS.”
PROVISIONAL SPECIFICATION left by the said Arthur Smith at the Office
of the Commissioners of Patents on the 27th March 1882.
ARTHUR SMITH of Rookwood House Wickham Road Brockley in the County of
Kent "IMPROVEMENTS IN CARBONS FOR ELECTRIC LAMPS
"
My invention relates to the production of carbonaceous filaments or rods for use
in electric lamps which I effect by treatment of the. substances known as Furfurol
and Fucusol in the following manner.
.
For producing filaments for incandescent lamps I pass through the liquid
furfurol or fucusol hydrochloric acid gas, taking care to keep the material cool.
The black liquid thus produced I enclose between glass plates kept a little apart so
as to determine the thickness required, and after the material has set I remove one
of the plates and cut the thin sheet of material into narrow strips, I bend these
strips between suitable moulds to horseshoe form and expose them to boiling heat.
When the filaments have. hardened put them in a crucible and covering them
with carbon powder expose them to a high heat. For producing carbon rods the
furfurol or fucusol may be treated with the acid gas in a tube of the size required
for the carbon, and after it has set the rod may be pushed out and subjected to
heat in the like manner. The electric resistance of the filament or rod may be
varied by mixing with the furfurol or fucusol before treatment with the acid gas a
greater or less proportion of carbon in a finely divided state, as for example lamp
black. Instead of employing hydrochloric acid gas, strong liquid sulphuric acid
may be used, this being mixed with the furfurol or fucusol. Instead of treating
pure furfurol or fucusol as above described, a less pure material may be used in
the following manner. I treat vegetable fibre such as jute with sulphuric acid of
a strength about 5 per cent at a temperature of 112° to 130° Fahr. so as to produce
dextrine and after concentration of this dextrine I act on it with strong acid
producing a black carbonaceous matter which can be dealt with in the same
manner as the product from furfurol or fucusol."

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Arthur Smith in the Great Seal Patent Office on the 26th September
1882.
ARTHUR SMITH of Rookwood House Wickham Road Brockley in the County of
Kent "IMPROVEMENTS IN CARBONS FOR ELECTRIC LAMPS".
My Invention relates to the production of carbons for electric lamps.in the form
of filaments of high resistance for incandescent lamps or of rods for are lamps.
For producing filaments I pass through the liquid Furfurol or Fucusol hydrochloric
acid gas in excess taking care to keep the liquid cool. The reaction produces a
black liquid which I enclose between two glass plates kept apart at a distance
equivalent to the desired thickness of filament for which purpose pieces of wire or
thread of equivalent diameter may be interposed between the plates. After the
material has thoroughly set which requires from 8 to 12 hours I carefully wedge
the plates apart and place that to which the film adheres in cold water for about
half an hour in which time the sheet of carbon will detach itself. This sheet is
then floated on to a flat surface of wood or cardboard which may be cemented on a
sheet of plate glass by shellac varnish. The excess of moisture is removed by
blotting paper and the adhering sheet is cut into strips of any required width by a
sharp knife. I bend these strips between moulds of horse-shoe or other suitable
form made of plaster of paris and expose them to a temperature of 212º. A
number of the strips may be bent together round a glass tube with their ends
secured by two threads passed outside and inside the tube longitudinally. The
strips thus bent form elastic rings of carbon. The filaments when removed from
the moulds or the glass tube are subjected to a high heat in closely covered
crucibles surrounded with carbon powder, or in porcelain tubes partly filled with
carbon powder through which a current of coal-gas is passed during the process.
According to another method, I pour on the glass plate a mixture of about
3 parts of Furfurol or Fucusol with 1 part of commercial vitriol of specific gravity
about 1.84 and when the material is set I treat it as before described.
The electrical resistance of the filaments may be varied by mixing about 22 per
cent of Lamp-black with the Furfurol or Fucusol before treatment.
For producing carbon rods for Are Lamps I mix Lamp-black or any finely
divided carbon with about 60 or 70 per cent. of Furfurol or Fucusol and subject
the mixture to compression in slightly tapered moulds, or force the pasty mass
through a die. Or according to another method, dry Lamp-black may be strongly
compressed into moulds so as to form rods which on being dipped for a moment in
a bath of Furfurol or Fucusol become thoroughly impregnated therewith. The
moulded or impregnated rods are then subjected to an atmosphere of hydrochloric
acid gas in vessels or tanks which may be made of Wood or Slate saturated with
paraffin. After remaining from 12 to 24 hours exposed to the gas they are 4
removed and, if necessary, they may be saturated by being dipped a second time
into the Furfurol or Fucusol, and again exposed to the acid gas. Such cracks as
may appear in the rods may be filled with a paste of carbon and Furfurol or
Fucusol. The rods are finished as usual by highly heating them in close vessels
in which they are covered with charcoal powder.
Although I have mentioned Hydrochloric Acid gas as the reagent employed
other Hydrogen Acids such as Hydro-fluoric, Hydriodic or Hydrobromic acid may
be employed but these are more expensive and less convenient in use.
4

page_text: Having thus described the nature of my invention and in what manner the
same is to be performed, I claim:
The manufacture of carbons for electric lamps by the treatment of Furfurol or
Fucusol substantially as herein described.
In witness whereof I the said Arthur Smith have hereunto set my hand and
seal this Twenty fifth day of September in the year of our Lord One
thousand eight hundred and eighty two.
ARTHUR SMITH. (L.S.)