IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC LAMPS
Year: 1880

page_text: LETTERS PATENT to Joseph Wilson Swan, of the Town and County of
Newcastle upon Tyne, Chemist, for an Invention of "IMPROVEMENTS IN AND
CONNECTED WITH ELECTRIC LAMPS."
PROVISIONAL SPECIFICATION left by the said Joseph Wilson Swan at the
*Office of the Commissioners of Patents on the 2nd December 1880.
JOSEPH WILSON SWAN, of the Town and County of Newcastle upon Tyne,
Chemist. "IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC LAMPS."
My Invention relates to that type of electric lamp in which light is produced
by the incandescence (by the passage of an electric current) of a conductor of
carbon enclosed in a glass vessel from which the air has been exhausted, and my
Invention consists chiefly of improvements in the carbon conductor itself and in
the mode of attaching it to its connexions.
In carrying out my Invention I form the conductor from cotton thread which
has been subjected to the action of sulphuric acid, in a manner similar to that
which is adopted in the production of vegetable parchment, as described in the
Provisional Specification accompanying my application for Letters Patent, dated
the 27th November 1880, No. 4933. I take cotton thread thus prepared or con-
verted and place it in a crucible or covered vessel containing carbon, such, for
example, as charcoal or any other suitable powder, which will prevent the oxidation
of the contents, and cover or enclose the suitably shaped converted cotton thread
with or in such carbon or powder, and I then introduce the crucible or vessel into
a kiln or oven and subject the whole to an elevated temperature. The converted
cotton thread thus becomes carbonized, and is then ready for use in the lamp.
In order to facilitate the connection between the carbons and the other con-
ductors to which they are to be attached the converted cotton thread previously
to its carbonization, as herein before described, may be wrapped at the ends with
strips of bibulous paper, muslin, or other suitable form of cotton or other material
susceptible of being converted, as before mentioned, so as to thicken it at the parts
where the attachment is to be effected; the thread thus thickened is then subjected
to the action of sulphuric acid in the manner before referred to, and (having been
washed and dried) may be compressed and shaped into arches, spirals, or other

page_text: forms adapted to the lamp required, after which it is subjected to the carbonizing
process hereinbefore described.
In lieu of covering or wrapping the converted cotton thread at the ends with.
bibulous paper or other suitable material, as herein before described, in order to
effect an intimate union of the ends of the carbon with the conducting wires, I
sometimes proceed as follows:-I cause the ends of the thread and the conducting
wires to overlap, and bind together such overlapping portions with fine wire and
thread or other material, as before described, or with thread, muslin, bibulous
paper, or other similar material without the wire; the thread so treated is then
subjected to the action of sulphuric acid, as before explained, and (after washing
and drying) is shaped to the required form and submitted to the carbonizing
process herein before described.
In order to further conduce to an efficient contact between the ends of the
carbons and the metallic conductors which support them I form the ends of the
said metallic conductors into either flat or tubular clips, compressed upon the ends
of the carbon by means of a ring or band fitting on the outside, so as to ensure
close contact between the carbon and the conductor; this contact may also be
improved by the interposition of a cushion of metallic leaf.
As a preliminary process in the preparation of the cotton thread I by preference
compress it by passing it through a die, or through plates, or by pressing it in a
mould, or by rolling it through rollers in order to render the thread perfectly
uniform in texture and section throughout its length, these conditions being
indispensable to the durability of the carbon.
I also sometimes increase the superficial area of the thread by flattening it,
whereby a larger extent of radiating surface is obtained, and consequently a greater
amount of light from a given current.
I also may construct the carbons of compound threads formed by taking a small
thread (converted by the action of sulphuric acid) as a core, and winding round it
spirally a number of other threads either in their natural condition or after they
have been subjected to the said converting process, the compound thread thus
formed being then submitted to the said converting process or not previously to
its carbonization in the manner hereinbefore explained; or in lieu of taking a
single thread I may lay a number of small threads together parallel with their axis,
so as to form a bundle, and subject this compound thread to the process of con-
version as before, so as to unite them together in one homogeneous mass, or I may
simply lay the threads side by side and unite them together laterally by subjecting
them to the converting process as before, a tape like form of carbon being
produced in the latter case, which provides a large superficial area and extent of
radiating surface.
In all cases I prefer to thicken the ends of the carbons in the manner herein-
before described.
I prefer to carry on the conversion of the threads in vacuo.
I sometimes employ in a single lamp multiple carbons of a curved form either of
the same or different lengths, and so arranged that either one or more may be
rendered incandescent at the same time. This arrangement admits of the degree
of light being varied as required, and also of readily bringing a spare carbon or
carbons into action in the event of the fracture of one or more of the carbons
which are in use.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Joseph Wilson Swan in the Great Seal Patent Office on the 1st
June 1881.
JOSEPH WILSON SWAN, of the Town and County of Newcastle upon Tyne,
5 Chemist. IMPROVEMENTS IN AND CONNECTED WITH ELECTRIC LAMPS."
56
My said Invention relates to that type of electric lamp in which light is pro-
duced by the incandescence (by the passage of an electric current) of a conductor of
carbon enclosed in a glass bulb or receptacle from which the air has been exhausted,
and my Invention consists chiefly of improvements in the carbon conductor itself
and in the mode of attaching it to its connections.
These improvements I shall now proceed particularly to describe by the aid of
the Sheet of Drawings hereunto annexed.
In carrying out my said Invention I form the conductor from cotton thread
which has been subjected to the action of sulphuric acid diluted with water in a
manner similar to that which is adopted in the production of vegetable parchment
from bibulous paper, as described in the Specification to former Letters Patent
granted to me, dated the 27th November 1880, No. 4933. I take cotton thread thus
prepared or converted and place it in a crucible or covered vessel containing
carbon, such, for example, as charcoal or any other suitable powder, which will
prevent the oxidation of the contents, and cover or enclose the suitably shaped
cotton thread with or in such carbon or powder, and I then introduce the crucible
or vessel into a kiln or oven and subject the whole to an elevated temperature. The
converted cotton thread thus becomes carbonized and is then ready for use in the
lamp.
In the Specification to my said former Letters Patent I have described a mode
of thickening the ends of the carbons by uniting material to the cotton thread by
immersion in sulphuric acid, the object of such increased thickness in the termina-
tions being to facilitate the connection between the carbons and the metallic
conductors to which they are to be attached, and by that means to prevent the
development of heat at the points of contact. According to my present Invention
I obtain this increased thickness of the terminations of the carbons in a peculiar
manner, as next hereinafter described.
I wrap the ends of the converted cotton thread a (Figure 1 and enlarged view
Figure 1) with strips of bibulous paper, muslin, or other suitable form of cotton
or other material susceptible of being converted, as before mentioned. The con-
verted cotton thread thus thickened, as shewn at b, is then subjected to the action
of sulphuric acid in the manner before referred to, and (having been washed and
dried) may be compressed and shaped into arches or spirals (an example of which
is shewn at c in Figure 1), or into other forms adapted to the lamp required, after
which it is subjected to the carbonizing process hereinbefore described.
In lieu of simply covering or wrapping the converted cotton thread at the ends
with bibulous paper, or other suitable material, as hereinbefore described, and in
order to effect an intimate union of the ends of the carbons with the metallic
conductors, I sometimes proceed in the following manner, viz.:-I cause the ends of
the thread a (Figure 2) and the conducting wires d to overlap, and I bind together
such overlapping parts with fine wire, as shewn at e, and thread or other material
as hereinbefore described, or with thread, muslin, bibulous paper, or other similar
material without the wire; the thread so treated is then subjected to the action of
sulphuric acid, as before explained, and (after washing and drying) is shaped
to the required form and submitted to the carbonizing process hereinbefore
lescribed.

page_text: When the last hereinbefore described method of effecting an efficient contact
between the ends of the carbons and the metallic conductors which support them is
not employed, I connect the thickened ends of the carbons with the said metallic
conductors by the employment either of flat clips f, as shewn in end and side
elevation and plan, Figures 3, 3, and 3b respectively, or tubular clips f, as indicated!
in elevation and plan in Figures 4 and 4*, the flat or tubular clip being used
according as the end of the carbon is of a flat or round section. These clips are
compressed upon the ends of the carbon a by means of a ring or band g fitting on
the outside so as to ensure close contact between the carbon and the conductor;
this contact may also be improved by the interposition of a cushion of metallic
leaf.
Figures 5 and 6 represent vertical sections taken at right angles to each other
of a lamp having applied to it the carbon illustrated in Figure 1, the ends of which
are secured in the clip illustrated in Figures 3, 3, and 3b. The conducting wires d
are represented as coated with glass or enamel, as described in the Specification to
former Letters Patent granted to me dated the 20th January 1880, No. 250, this
arrangement being found desirable in practice in order to prevent ingress of air and
to guard against the evolution of gas from the wires themselves. When the two
conducting wires can be conveniently brought into proximity, as indicated in
Figure 2, they may be enclosed in a glass or enamel stem h, common to the two
but bifurcated at its upper extremity as shown.
I sometimes employ in a single lamp multiple carbons of a curved form, either of
the same or different lengths, and so arranged that either one or more may be
rendered incandescent at the same time. An example of this arrangement is
illustrated in elevation and plan in Figures 7 and 8 respectively.
In this example two carbons are employed, arranged respectively at right angles
to each other, and marked a, a¹; one end of each of these carbons is attached to a
conducting wire d common to the two, the said ends entering respectively sockets
3, 4, carried by the wire d; the other ends of the two carbons a, a', are respectively
attached to other wires d', d², by entering sockets 5, 6, in a similar manner. By
connecting therefore either or both of the wires d¹, d², with the source of electricity
either of the carbons a, a', may be used separately or both may be used in
conjunction, as desired.
Similarly a greater number than two carbons may be applied to a single lamp,
any one or more of which may be used separately, or all of which may be used in
conjunction.
This arrangement admits of the degree of light being varied as required, and
also of readily bringing a spare carbon or carbons into action in the event of the
fracture of one or more of the carbons which are in use.
As a process in the preparation of the cotton thread preliminary to carbonisation
after treatment with acid I, by preference, compress the converted cotton thread
by passing it through a die or through plates, or by pressing it in a mould, or by
rolling it through rollers in order to render the thread perfectly uniform in texture
and section throughout its length, and to make the thickened ends more uniform
in shape and size and more solid, these conditions being indispensable to the
durability of the carbon.
I also sometimes increase the superficial area of the converted thread by flattening
it, whereby a larger extent of radiating surface is obtained, and consequently a
greater amount of light from a given current.
I also may construct the carbons of compound threads formed by taking a small
thread 1, Figure 9 (converted by the action of sulphuric acid) as a core, and winding
round it spirally a number of other threads 2, either in their natural condition or
after they have been subjected to the said converting process, the compound thread
thus formed being then submitted to the said converting process or not previously
to its carbonization in the manner hereinbefore explained. Or in lieu of taking a
single thread I may lay a number of small threads 1 together parallel with their
axes so as to form a bundle, as shewn in Figure 10, and subject this compound

page_text: thread to the process of conversion as before so as to unite them together in one
homogenous mass, or I may simply lay the threads side by side, as indicated in
Figure, 11, and unite them together laterally by subjecting them to the converting
process as before, a tape like form of carbon being produced in the latter case
which provides a large superficial area and extent of radiating surface.
In all cases I, by preference, thicken the ends of the carbons in the manner
hereinbefore described.
I prefer to carry on the conversion of the threads in vacuo.
Having now described and particularly ascertained the nature of my 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 claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,-
First. Forming the carbon or carbons of an electric lamp from cotton thread
converted by the action of sulphuric acid and carbonized by subjecting it to heat
in a vessel or receptacle containing powdered carbon or other powder which will
prevent the oxidation of the material under treatment, substantially as hereinbefore
described.
Second. Constructing carbons formed from cotton thread with thickened
terminations by wrapping the ends with strips of bibulous paper, muslin, or other
suitable material, as herein set forth, and then submitting the cotton thread so
treated to the action of sulphuric acid, and afterwards carbonizing it by subjecting
it to heat in a vessel or receptacle containing powdered carbon or other powder
which will prevent the oxidation of the material under treatment, substantially as
hereinbefore described.
Third. Binding the ends of the cotton thread to the conducting wires, as herein
set forth, and subjecting the same to the converting and carbonizing processes,
substantially as herein before described.
Fourth. In the production of carbons for electric lamps from cotton thread,
compressing the converted cotton thread so as to render it perfectly uniform in
texture and section throughout its length, substantially as hereinbefore described.
Fifth. In the production of carbons for electric lamps from cotton thread
Battening the converted cotton thread in order to obtain an increased superficial
area, substantially as hereinbefore described.
Sixth. Constructing the carbons of compound threads, substantially as herein-
before described.
In witness whereof, I, the said Joseph Wilson Swan, have to this my
Specification set my hand and seal, the Twenty third day of May, One
thousand eight hundred and eighty one.
JOSEPH WILSON SWAN. (L.S.)