IMPROVEMENTS IN ELECTRIC LAMPS AND IN THE METHOD OF MANUFACTURING THE SAME
Year: 1879

page_text: LETTERS PATENT to Thomas Alva Edison, of Menlo Park, in the State of New
Jersey, United States of America, for the Invention of "IMPROVEMENTS IN
ELECTRIC LAMPS AND IN THE METHOD OF MANUFACTURING THE SAME."
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 15th December 1879.
"
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United
States of America. IMPROVEMENTS IN ELECTRIC LAMPS AND IN THE METHOD OF
MANUFACTURING THE SAME."
In a former application made by me for Letters Patent in Great Britain an
unprovement in electric lamps is set forth, wherein a filament of carbon is enclosed
in a glass bulb and the atmosphere removed as nearly as possible, and the carbon
is brought to incandescence by an electric current to form the lamp.
My present Invention relates to an improvement in the process of manufacturing
the carbon filament and the means for securing the same to the conductors.
I make use of paper of the desired thickness, as free as possible from foreign
substances or adulterations, and for this purpose I prefer and use bristol board.
With suitable instruments, such as a punch and die, I cut out a narrow strip of this
paper, preferably in the form of an elliptical bow or an arc of a circle, the ends of
the strip being by preference wider than the other portions.
A number of these pieces of paper are laid flat wise in the bottom of a mould,
preferably of wrought iron, and there is laid on them a light weight in the form of
a flat piece of gas retort carbon or other device that will not be distorted by the
heat. If several of these are laid one on the other in the mould a piece of tissue
paper is interposed between each one and the next. A cover is used to close the
mould, and the mould is raised very gradually to a temperature of about six
hundred degrees Fahrenheit. This allows the volatile portions of the paper to pass
away, and at the same time the mould retains the paper in its proper shape and
the paper is prevented from curling up or becoming distorted, as it would be
likely to do if the heat was applied suddenly or the light weight dispensed with.
The mould is now placed in a furnace and heated almost to a white heat, and
then removed and allowed to cool gradually.

page_text: The carbon filaments will be found to be smaller than the cardboard blanks, and
to be sufficiently strong and flexible for handling. The ends of the carbon are to
be secured to the metallic conductors in any convenient manner.
The carbon filaments prepared as aforesaid are very uniform in their resistance
to the electric current, and I make them thin and of a sufficient length to offer u
great resistance to the passage of the current. The clamps that connect the con-
ductors to the ends do not require to be pressed with much force on the carbon,
because the resistance to the passage of the current between the clamp and the
carbon will be less than the resistance of the carbon filament, hence but little heat
will be developed at the clamps. In ordinary electric lamps the large carbons do
not offer much resistance to the electric current, and unless the clamps are very
firmly pressed upon the carbon the current meets with considerable resistance at
the clamps, and hence heat is developed at such clamps.
The clamps that I prefer are made of a steel spring tipped at the ends with
platina or similar metal. The spring is bent into a circle or bow, and the ends
crossed and turned back towards each other, similar in shape to the figure 8, with
the opening for the carbon between the spring ends at the upper part; the object
of this shape is that the pressure of the clamps on the carbon may be increased by
the expansion of the spring by the heat of the lamp instead of being lessened, as it
would be if the wire was only bent into a single bow.
The spring clamps are connected to the platina or similar conducting wires by
clips, and the platina wires pass through the glass of the globe or bulb that contains
the lamp; the air is to be exhausted from the bulb by any suitable means, and it is
preferable to exhaust said air as perfectly as possible, say to the one eight hundred
thousandth of an atmosphere.
The lamps are suspended or supported in any convenient manner and the electric
current from a magneto electric machine or other source of electricity is passed
through the lamp and brings the carbon filament to a high incandescence, and the
lamp is very durable, and a large number of such lamps can be placed in the electric
circuit in multiple arc or otherwise, as desired.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Alva Edison in the Great Seal Patent Office on the 15th
June 1880.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United
States of America. "IMPROVEMENTS IN ELECTRIC LAMPS AND IN THE METHOD OF
MANUFACTURING THE SAME."
In British Letters Patent, No. 4576 granted to me November 10, 1879, an
improvement in electric lamps is set forth wherein a filament of carbon is inclosed
in a glass bulb and the atmosphere removed as nearly as possible, and the carbon
is brought to incandescence by an electric current to form the lamp. My present
Invention relates to an improvement in the process of manufacturing the carbon
filament, and in the means for securing the same to the conductors. I make use of
paper of the desired thickness, as free as possible from foreign substances or
adulterations, and for this purpose I prefer and use "bristol board." With suitable
instruments, such as a punch and die, I cut out a narrow strip of this paper,
preferably in the form of an elliptical bow or an are of a circle, the ends of the strip
being by preference wider than the other portions A number of these pieces of
paper are laid flatwise in the bottom of a mold, pieferably of wrought iron, and
there is laid on them a light weight in the form of a flat piece of gas retort carbon
or other device that will not be distorted by the heat. If several of these are laid
one on the other in the mold a piece of tissue paper is interposed between each one
and the next. A cover is used to close the mold, and the mold is raised very
gradually to a temperature of about six hundred degrees Fahr. This allows the
volatile portions of the paper to pass away, and at the same time the mold retains
the paper in its proper shape and the paper is prevented from curling up or
becoming distorted, as it would be likely to do if the heat was applied suddenly or
the light weight dispensed with. The mold is now placed in a furnace and heated
almost to a white heat, and then removed and allowed to cool gradually. The carbon
filaments will be found to be smaller than the cardboard blanks, and to be
sufficiently strong and flexible for handling. The ends of the carbon are to be
secured to the metallic conductors in any convenient manner. The carbon filaments
prepared as aforesaid are very uniform in their resistance to the electric current,
and I make them thin and of a sufficient length to offer a great resistance to the
passage of the current. The clamps that connect the conductors to the ends do not
require to be pressed with much force on the carbon, because the resistance to the
passage of the current between the clamps and the carbon will be less than the
resistance of the carbon filament, hence but little beat will be developed at
the clamps. In ordinary electric lamps the large carbons do not offer much
resistance to the electric current, and unless the clamps are very firmly pressed
upon the carbon the current meets with considerable resistance at the clamps and
hence heat is developed at such clamps. The clamps that I prefer are made of a
steel spring tipped at the ends with platina or similar metal; the spring is bent
into a circle or bow and the ends crossed and turned back towards each other,
similar in shape to the figure 8, with the opening for the carbon between the spring
ends at the upper part; the object of this shape is that the pressure of the clamps
on the carbon may be increased by the expansion of the spring by the heat of the
lamp instead of being lessened, as it would be if the wire was only bent into a
single bow. The spring clamps are connected to the platina or similar conducting
wires by clips, and the platina wires pass through the glass of the globe or bulb
that contains the lamp; the air is to be exhausted from the bulb by any suitable
means, and it is preferable to exhaust said air as perfectly as possible, say to the
one eight hundred thousandth of an atmosphere. The lamps are suspended or
supported in any convenient manner and the electric current from a magneto

page_text: electric machine or other source of electricity is passed through the lamp and brings
the carbon filament to a high incandescence, and the lamp is very durable, and a
large number of such lamps can be placed in the electric circuit in multiple arc or
otherwise, as desired.
In the Drawing,-
Fig. 1 is a vertical section of the lamp complete.
"
$1
2 is a side view in larger size of the clamping device.
3 is a section at the line x, x, in still larger size.
4 is the wire forming one of the clamps before it is bent up to shape.
"
#
5 is the paper blank before it is carbonized, and
"
6 is a section of the box.
The blank a is cut out of paper material, such as "bristol-board," in the proper
shape, the form shown in Fig 5 is preferred; the same is laid in the metal mold b,
and when several are laid one on the other pieces of thin paper are introduced
between. The weight d is laid on these, it is to be heavy enough to prevent the
paper curling up under the action of the heat, but it allows the
as the volatile matters are expelled by the heat. This weight & is of
gas retort
carbon. The cover e is placed on the mold and secured, and the mold is heated as
before described.
paper
to contract
The carbon filament i forms the lamp when rendered incandescent by the electric
current passed through it. The clamp is made of the wire h, at the ends of which
are tips or small rivets r of platina or similar material. The wire is bent up and
crossed, as shown, so as to act as a spring in clamping the end of the carbon
filament that is placed within such clamp. The wire is attached to a small stock o,
into which the conducting wire t passes and is clamped.
The conductors for the two ends of the carbon are inserted into the glass and the
latter intimately melted around them, the carbon and clamps are connected to the
wires and the parts introduced within the neck of the bulb m and the glass melted
at v; the air is exhausted from the globe by the tube k that passes away, as shown
by dotted lines, and the tube melted together while the vacuum is maintained.
The lamp is ready for the conductors to be attached to it, and the carbon is
rendered incandescent by the current that passes through the same. It is durable
as there is nothing to combine with the carbon, and it is substantially
indestructible.
I claim as my Invention,―
First. An electric lamp formed of carbonized paper.
Second. The method herein specified of manufacturing carbons for electric lights,
consisting in exposing the filament of paper to the action of heat in a mold to drive
off the volatile portions and carbonize the paper, substantially as set forth.
Third. A carbon for electric lights made as a filament with the ends broader for
the clamping devices that connect the conductors.
Fourth. The clamp for the carbon of an electric lamp composed of a bow or
elliptical spring with the ends crossing each other and receiving between them the
carbon, substantially as set forth.
indestructible.
I claim as my Invention,―
First. An electric lamp formed of carbonized paper.
Second. The method herein specified of manufacturing carbons for electric lights,
consisting in exposing the filament of paper to the action of heat in a mold to drive
off the volatile portions and carbonize the paper, substantially as set forth.
Third. A carbon for electric lights made as a filament with the ends broader for
the clamping devices that connect the conductors.
Fourth. The clamp for the carbon of an electric lamp composed of a bow or
elliptical spring with the ends crossing each other and receiving between them the
carbon, substantially as set forth.
In witness whereof, I, the said Thomas Alva Edison, have hereunto set my
hand and seal, this Eighteenth day of May, A.D. 1880.
Witnesses,
STOCKTON L. GRIFFIN,
JOHN F. Randolph.
THOMAS ALVA EDISON. (LS)