IMPROVE- MENTS IN INCANDESCING CONDUCTORS FOR ELECTRIC LAMPS AND IN MOULDS FOR THE CARBONIZATION OF THE SAME
Year: 1882

page_text: LETTERS PATENT to Thomas John Handford of 42 Southampton Buildings
in the County of Middlesex Patent Agent for an Invention of IMPROVE-
MENTS IN INCANDESCING CONDUCTORS FOR ELECTRIC LAMPS AND IN MOULDS
FOR THE CARBONIZATION OF THE SAME Communicated to him from abroad
by Thomas Alva Edison of Menlo Park in the State of New Jersey United
States of America
PROVISIONAL SPECIFICATION left by the said Thomas John Handford
at the Office of the Commissioners of Patents on the 29th December 1882.
THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex Patent Agent "IMPROVEMENTS IN INCANDESCING CONDUCTORS FOR
ELECTRIC LAMPS, AND IN MOULDS FOR THE CARBONIZATION OF THE SAME
A communication to me from abroad by Thomas Alva Edison of Menlo Park
in the State of New Jersey United States of America
"
This Invention relates to the production of flexible carbon filaments for the
incandescing conductors of electric lamps which shall be of high resistance and
of even resistance throughout their length, and have great flexibility, and it
consists in forming the incandescing conductor for an electric lamp of a number
of fine continuous flexible carbon filaments massed together, so as to be in close
contact throughout the whole length and having their ends secured, the separate
filaments being capable of independent expansion, and contraction.
In carrying out the Invention it is prefered to take several long and very fine
fibres of the same or almost the same length such as those of Ramie, flax, and
similar vegetable substances and twist them tightly together, so as to form a fibrous
thread. The ends are secured preferably by a plastic carbonizable substance
attached to them such as a compound of carbon and sugar.
The filament thus formed is carbonized under strain or pressure, or both, and
may be bent either before or after carbonization into the desired form. The
plastic compound upon the ends of the filament may form enlarged ends for
clamping.
The ends of the twisted filament are then attached to the leading-in wires sealed
in the stem or tube of a lamp and are preferably electro-plated to such wires, the
filaments before electro-plating being again twisted tightly, so as to bring them all
in contact with each other throughout their entire length.

page_text: Instead of the process described the filaments may be carbonized straight and
separately, and such carbonized filaments be then twisted tightly together. The
ends are then attached to the leading-in wires preferably by electro-plating, the
filaments being kept tightly twisted during this process.
The filament formed in either of the above ways and attached to the leading-in
wires is placed in the globe of a lamp in the usual manner and is ready for the
exhausting process.
While as stated it is preferred to use natural vegetable fibres, it is evident that
a conductor of the kind described may be formed of other substances, such as
cellulose, paper, parchment, fine thread, treated with hydrofluoric acid and the
like, fine filaments of such substances being twisted together as described.
Filaments may it is evident be braided or otherwise intertwined, instead of
twisted together.
Filaments formed as described are of unusually even resistance and incan-
descence as each of the separate filaments is continuous, extending the whole
length of the filament.
The filament is also exceedingly flexible and elastic, and therefore well adapted
for the purpose for which it is to be used.
This flexibility arises from the fact that the carbon filament is formed of a
number of separate fine filaments which are capable of independent contraction
and expansion.
This fact also makes the filament less liable to fracture from unequal expansion
and contraction, which must occur with a carbon filament made as a single mass,
since it is not possible to produce a filament of this latter character which will be
absolutely homogenous. In order to preserve the independent character of the
fine filaments of which the complete filament is inade up it is essential that no
carbonizable material should be placed upon the body of the carbon filament, nor
should the carbon filament, or the material from which it is made by carbonization,
be so treated as to cause the fine filaments to cohere.
Another part of the Invention relates to the manufacture of such conductors, the
object being to provide a mould for holding them during carbonization, which will
keep them straight, allow contraction, and prevent the filaments from untwisting.
While the Invention is adapted for use with the twisted filaments described it
may also be employed in carbonizing any straight filaments for the purpose
mentioned
The improved mould consists of a shallow receptacle of suitable length and
width made of carbon, nickel, or other material capable of withstanding high
temperatures. It is provided at one end with a vertical dovetail slot, opening
into the interior of the mould and preferably not extending quite to the bottom
of the same.
At the other end of the mould there is a movable block provided
with a similar slot.
The enlarged ends of the filament are placed in the slots, and the block is moved
to place the filament under tension. The inould has a suitable cover. During the
process of carbonization, the contraction of the filament is permitted by the movable
block which keeps the filament under constant strain
Instead of one moveable block, two may be used, one at each end of the mould
in which case both blocks would be moved by the contraction of the filament. The
slots not extending quite to the bottom of the mould the filament will be supported
out of contact with the bottom of the mould.
It is evident that a number of filaments can be placed in the slots one above
the other, if the depth of the mould is increased, but it is preferred to place one
filament only in each mould.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas John Handford in the Great Seal Patent Office on the
28th June 1883.
THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex, Patent Agent "IMPROVEMENTS IN INCANDESCING CONDUCTORS FOR
ELECTRIC LAMPS, AND IN MOULDS
FOR
THE
THE CARBONIZATION OF
SAME
"
A communication to me from abroad by Thomas Alva Edison of Menlo Park
in the State of New Jersey, United States of America.
This Invention relates to the production of flexible carbon filaments for the
incandescing conductors of electric lamps, which shall be of high resistance, and of
even resistance throughout their length and have great flexibility; and it consists
partly in forming the incandescing conductor for an electric lamp, of a number of
separate continuous flexible carbon filaments, the same being natural vegetable
fibres, massed together, so as to be in close contact throughout the whole length and
having their ends secured together whilst the separate filaments are capable of
independent expansion and contraction.
In carrying out the Invention I take several long and fine fibres of the same or
almost the same length such as those of Ramie, flax, and similar vegetable
The
substances, and twist them tightly together so as to form a fibrous thread.
ends are secured preferably by a plastic carbonizable substance attached to them
such as a compound of carbon and sugar.
The
The filament thus formed is carbonized under strain, or pressure, or both and
may be bent either before or after carbonization into the desired form.
plastic compound upon the ends of the filament may form enlarged ends for
clamping
The ends of the twisted filament are then attached to the leading-in wires sealed
in the stem or tube of a lamp and are preferably electroplated to such wires, the
filaments before electroplating being again twisted tightly, so as to bring them all
in contact with each other throughout their entire length.
Instead of the process described, the filaments may be carbonized straight, and
separately, and such carbonized filaments be then twisted tightly together. The
ends are then attached to the leading-in wires preferably by electroplating, the
filaments being kept tightly twisted during this process.
The filament formed in either of the above ways and attached to the leading-in
wires, is placed in the globe of a lamp in the usual manner and is ready for the
exhausting process.
This part of the Invention is illustrated in figures 1, and 2, of the drawings
Figure 1, is a view of an incandescing electric lamp embodying the Invention ;
and
Figure 2 represents a portion of the twisted filament the size thereof being of
course greatly exaggerated.
A, is the enclosing globe, and B the inner stem through which pass the leading-in
wires 1, 2, to which are attached the ends of the carbon filament C, which is formed
of a number of individual filaments c, c, twisted together, and secured together at
their ends by a plastic substance a.
The separate filaments are formed of natural vegetable fibres.
The several filaments are twisted before or after carbonization and are capable
of independent contraction and expansion, no material being used, or no treatinent
being resorted to which will cause the several fine filaments to cohere.
lu lieu of securing the ends of the separate continuous filaments by a plastic
compound, they may be electro-plated together after carbonization; or the filaments

page_text: may be twisted together and carbonized without any special bolding together at
the ends, and then inserted in the clamps and secured by electro-plating or
otherwise.
--
For example, a convenient mode of making the filament is the following:-
A number of vegetable fibres of twice the length desired are taken, and twisted
together; they are then doubled and the twist locks itself; the compound filament
thus partially formed is next carbonized, and the ends electro plated. and inserted
in clamps, or the filament may be inserted in clamps without previously electro-
plating the ends. The ends consolidated by the application of carbon may be used
instead of the electro-plated ends.
In lieu of the filaments being twisted together they may be braided or otherwise
intertwined before or after carbonization.
Filaments formed as described are of unusually even resistance and incandescence
as each of the separate filaments is continuous, extending the whole length of the
filament
The filament is also exceedingly flexible and elastic and therefore well adapted
for the purpose for which it is to be used. This flexibility arises from the fact
that the carbon filament is formed of a number of separate fine filaments which are
capable of independent contraction, and expansion.
This fact also makes the filament less liable to fracture from unequal expansion
and contraction, which must occur with a carbon filament made as a single mass,
since it is not possible to produce a filament of this latter character which will be
absolutely homogenous. In order to preserve the independent character of the
fine filaments of which the complete filament is made up; it is essential that no
carbonizable material should be placed upon the body of the carbon filament, nor
should the carbon filament, or the material from which it is made by carbonization,
be so treated as to cause the fine filaments to cohere.
The invention also relates to the manufacture of such conductors, the object
being to provide a mould for holding them during carbonization, which will keep
them straight, allow contraction, and prevent the filaments from untwisting.
While the Invention is adapted for use with the twisted filaments described, it
may also be employed in carbonizing any straight filaments for the purpose
mentioned.
The improved mould consists of a shallow receptacle of suitable length and
width, made of carbon, nickel, or other material capable of withstanding high
temperatures. It is provided at one end with a vertical dovetail slot, opening into
the interior of the mould, and preferably not extending quite to the bottom of the
same. At the other end of the mould there is a movable block provided with a
similar slot. The enlarged ends of the filament are placed in the slots, and the
block is moved to place the filament under tension. The mould has a suitable
cover.
During the process of carbonization the contraction of the filament is permitted
by the movable block, which keeps the filament under constant strain.
This part of the Invention is illustrated in figures 3, and 4, of the drawings.
Figure 3, is a sectional view of the carbonizing mould; and
Figure 4, a perspective view of the same.
The carbonizing mould for receiving the filament A, consists of a box B, formed
of carbon, nickel, or other material capable of withstanding high temperatures.
In one end is formed a slot b of such size, and shape as to receive the enlarged
end of the filament
At the other end of the mould is set a movable block C, provided with a slot c,
similar to slot b. The block C, may be of carbon, or of nickel or of nickel covered
with carbon; it must however have sufficient weight to keep the filament
stretched.
The slots, b, c, do not extend quite to the bottom of the mould, and the filament
for carbonization is placed in the mould from above with its ends resting in the
bottoms of the slots, and its body kept out of contact with the mould. The
7

page_text: filament is kept taut in the mould, which is placed in the carbonizing furnace, a
suitable cover being provided. As the filament contracts, the movable block C
slides toward the centre of the mould, keeping the filament still tightly stretched,
and preventing the fibres from untwisting.
It is obvious that two movable blocks instead of one may be employed the same
sliding toward each other as the carbon contracts. Since the slots do not extend
quite to the bottom of the mould, the filament will be supported out of contact
with the bottom of the mould.
It is also evident that the mould described can be used for any straight
filaments, to allow contraction during carbonization. Filaments formed in this
manner are preferably bent into a loop before being placed in the lamp.
Any desired number of filaments may of course, be placed one above another in
the carbonizing mould if the depth of the mould is increased, but it is preferred to
place one filament only in each mould.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original
and therefore clain as the Invention secured to me by the hereinbefore in part
recited Letters Patent, is:-
First. The flexible carbon filament, for an incandescing electric lamp, formed of
a number of separate continuous filaments consisting of natural vegetable fibres,
secured together, and each capable of independent expansion and contraction,
substantially as herein before described.
Second. The mould for the carbonization of straight filaments, substantially as
herein before described.
In witness whereof I the said Thomas John Handford have hereunto set my
band and seal this twenty eighth day of June in the year of our Lord,
one thousand eight hundred and eighty three.