IMPROVEMENTS RELATING TO THE PRODUCTION OF THE ELECTRIC LIGHT, IN ELECTRIC LAMPS, IN THE MEANS FOR AND METHODS OF MANUFACTURE OF THE CARBONS AND INCANDESCING CONDUCTORS FOR THE SAME.
Year: 1881

page_text: LETTERS PATENT to Alfred Richard Sennett, of Worthing, in the County
of Sussex, Engineer, for an 'Invention of "IMPROVEMENTS RELATING TO
THE PRODUCTION OF THE ELECTRIC LIGHT, IN ELECTRIC LAMPS, IN THE
MEANS FOR AND METHODS OF MANUFACTURE OF THE CARBONS AND
INCANDESCING CONDUCTORS FOR THE SAME.'
"
PROVISIONAL SPECIFICATION left by. the said Alfred Richard Sennett at
the Office of the Commissioners of Patents on the 3rd December 1881.
ALFRED RICHARD SENNETT, of Worthing, in the County of Sussex, Engineer.
"IMPROVEMENTS RELATING TO THE PRODUCTION OF THE ELECTRIC LIGHT, IN
ELECTRIC LAMPS, IN THE MEANS FOR & METHODS OF MANUFACTURE OF THE
CARBONS & INCANDESCING CONDUCTORS FOR THE SAME.”
My Invention has for its object improvements relating to the production of the
electric light, more especially with reference to that system in which it is obtained
by the incandescence of a continuous conductor enclosed in a vacuous receiver.
Firstly, in the preparation & production of a conductor more uniform in its
specific electrical resistance, and better adapted to withstand the very high
temperature to which it must necessarily be subjected, & to the disintegrating
action of the residual gas of the receiver. Secondly, in the method of compressing
& compacting the same so as to render it extremely dense & imporous. Thirdly,
in the method of carbonizing the same. Fourthly, in the method of mounting the
same. Fifthly, in the method of eliminating the atmospheric air from the receiver.
Sixthly, in the method of making the joint between the material of the receiver
& of the conductors.
To obtain these objects, I reduce any material sufficiently pure & containing
a high per centage of cellulose to a finely divided jelly-like state or pulp (either
fibrous or otherwise) by chemicals or other means. In this condition the whole of
the impurities so detrimental to the durability of the conductor can most conveniently
be removed by the usual chemical means; from this I form by moulding or other
operation the required conductors.

page_text: In order to produce the requisite hardness & compactness I mould or form the
conductor under great pressure, whilst to ensure its imporosity I cause this operation
to take place (very slowly) in a vessel from which the air is being constantly
exhausted. In the methods of carbonizing hitherto made use of, although the
external air is prevented from combining with the carbon by filling the chamber or
crucible with powdered carbon, the occluded gases still remain to exert their
injurious effect, for any air remaining within the substance of the conductor during
the process of carbonization will cause loss of carbon to take place by the formation
of carbonic-dioxide & the porosity of the conductor (& consequently the uniformity
in its specific electrical resistance) will be greatly affected, the former being
increased whilst the latter is diminished. In some methods of manufacturing, the
conductors after having been carbonized in the usual manner, are heated to white-
ness in a hydro-carbon vapour, & this being decomposed deposits carbon (both
internally & externally upon the conductor.) Now this deposited carbon how-
ever differs both in its co-efficient of expansion, & in its specific electrical resistance
from that upon which it is deposited. Obviously then the structure of the conductor
is not in accordance with the required conditions. In order to prevent this & to
obtain an extremely homogeneous conductor I place the highly compressed material
in a suitable carbonizing chamber in which I produce (while cold) a vacuum, the
effect of which is to cause the occluded gases (if any) to be partially driven out by
their own expansive force, & to completely displace them I pass a suitable vapour
or inert gas through the chamber which is then healed up to the temperature
required for the carbonization of the material.
The method of mounting the incandescing portion of the conductor consists in
forming the enlargements upon the ends thereof (if they have not previously been
formed in the primary operation) in a way precisely analogous to that already
explained. In the ordinary methods of enlargening the ends a very great & abrupt
increase in the sectional area of the conductor takes place, & this giving rise to
great differences of temperature ultimately produces fracture of the conductor. To
obviate this I make the end of this enlargement take somewhat the form of an
acute pyramid, the sides of which however are curved so that all contiguous portions
have but slightly different temperatures. These enlargements may be used for
connecting metallic wires thereto, which may be sealed into the material of the
receiver by the ordinary method (Geissler), or they may be prolonged so as to form
the supports for the incandescing portion & be themselves (after suitable treatment
which I do not bere describe) sealed into the material of the receiver.
In order thoroughly to eliminate all the atmospheric air contained in the receiver
I first exhaust & then pass a stream of some suitable vapour (other than hydro-
carbon) or inert gas through receiver, & then re-exhaust to the highest obtainable
degree, consequently the slight residual trace is of a perfectly harmless nature.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alfred Richard Sennett in the Great Seal Patent Office on the
3rd June 1882.
ALFRED RICHARD SENNETT, of Worthing, in the County of Sussex, Engineer.
"IMPROVEMENTS RELATING TO THE PRODUCTION OF THE ELECTRIC LIGHT, IN
ELECTRIC LAMPS, IN THE MEANS FOR AND METHODS OF MANUFACTURE OF THE
CARBONS AND INCANDESCING CONDUCTORS FOR THE SAME."
My Invention has for its object improvements relating to the production of the
electric light, more especially with reference to that system in which it is obtained
by the incandescence of a continuous conductor contained in a vacuous receiver.
The first part of my Invention has for its object the preparation of the material of
the incandescing conductor, so as to render it very homogeneous in structure. To
obtain this I reduce any material sufficiently pure, and containing a high per
centage of cellulose to a finely divided jelly like form or pulp, and from this I
mould the conductor; linen cuttings, cotton, cotton wool, &c., are convenient
materials for this purpose. These I place in a machine and reduce them. This
may also be effected by the use of suitable chemicals, but by dividing the substance
mechanically the reduced material is fibrous in structure, which is not the case
when chemical solvents are employed. The interweaving of these fibres produces
a much more tenacious material. In order to mould the material into the required
forms by the process hereafter explained, it is necessary to obtain layers of the
material of uniform thickness. For this purpose I employ the depositing apparatus
shown in Fig 1. The material having been sufficiently reduced is allowed to run
into the vessel A. This vessel is separated from the chamber B by the porous
diaphragm D. The chamber B is connected by means of pipe C to an air pump.
By partially exhausting the air from the chamber B layers of the material of any
required thickness are quickly and conveniently deposited upon the diaphragm. I
am aware that incandescing conductors for electric lamps have been made from
paper, and that the process of mechanically dividing the material is somewhat
analagous to that employed in paper making, but the method of depositing the
pulp employed in paper making in itself destroys the homogeneity of the material
so essential to the longevity of the incandescing conductors of electric lamps. By
the method of depositing herein described, namely, upon a diaphragin of suitable
material pervious to water this defect is obviated. The material thus deposited has
next to be removed to the moulds. For this purpose the chamber E, the under sido
of which is perforated and covered with felt, is lowered into the vessel A. The
tube shown on the upper side of the chamber is connected to an air pump, and
upon this being set in action and air admitted beneath the diaphragm the material
may conveniently be removed to the moulds afore mentioned.
The second part of my Invention relates to the moulding, compressing, and
compacting of the material, so as to render it very hard and imporous and very
uniform in its specific electrical resistance. To effect this I place the material in
moulds or die plates constructed of suitable material to withstand great pressure, .
preferably steel or phosphor bronze, such as those shown in Fig 2. I then subject
it to great pressure, employing for this purpose a powerful hydraulic press. The
effect of this process is to impart to the material the required form, and also to
make it very dense and compact. In order to ensure its imporosity and to avoid
the possibility of any air being imprisoned within the material I employ both
pressure and exhaustion. The moulds or die plates afore mentioned are enclosed
in a chamber, from which the air is exhausted before the pressure is applied.
The pressure is applied and increased very slowly, and the air is continuously

page_text: exhausted during the operation. The material having been removed from the
moulds or die plates is shaped, into the required forms by cutting, punching, or
other suitable process. I find the following a convenient method of doing this.
The material moulded as explained, and having the form shewn at Fig. 3., is passed
under a fly press furnished with suitable cutters, which makes transverse cuts as
shown at a, a, b, b, c, c, d, d. It is then bent into any desired form over a suitable
template, as at Fig. 4, and placed in a clamp c, c, ready for insertion in the
carbonizing chamber hereafter explained. This is a convenient method for the
shaping of conductors designed for lamps of high resistance, but in lamps of low
resistance where the conductor is thicker it is better to shape the material into its
permanent form in order to avoid danger of producing a strain at the point of
bending. Again, in other forms it is advisable to have a mould or die plate for
each conductor. In the latter case the conductor is finished in the mould, no
subsequent cutting or punching process being necessary. In moulding rods for
electric arc lamps the same process of rendering the material very dense and
imporous is employed, it being applicable to any material. For this purpose the
moulds or die plates have planed in them grooves or slots having three equal sides,
so that when the plates are placed together the two grooves form a hexagonal hole.
By employing this form of section the danger of splitting the rods in opening the
mould is avoided. Instead of placing tho moulds within another vessel for the
purpose of exhausting the air from the material pieces of a suitable material (such
as certain woods, bamboos, &c., placed with their grain parallel to the axis of the
grooves) may be inserted at the ends of the grooves, the ends of the said grooves
or slots being connected to the exhausting apparatus.
The third part of my Invention relates to the method of carbonizing the
material. To prevent deterioration of the conductor by loss of carbon during the
process of carbonization, and also to allow for expansion and contraction, the
material (held in the clamps afore mentioned) is placed in the carbonizing chamber.
This is represented at A, Fig. 5, the furnace in which it is placed being shown by
b, b, b. The pipe 2 communicates with an air pump. Before heat is applied the
chamber is evacuated. The effect of this evacuation is to cause any gas occluded
within the material to be driven out by its own expansive force and to completely
Jisplace it. I pass through the chamber a stream of suitable vapour (other than
hydrocarbon) or inert gas. I find the vapour of the bi-sulphide of carbon very
effective. The method of employing it is shown in Fig. 5. The chamber is then
heated up to the temperature required for complete carbonization. After the
material has been removed from the chamber it is held in a suitable vice, and the
strengthening flanges shown at a, a, Fig. 4, are cut off by means of a rapidly
revolving circular saw or disc of celluloid; by this means the conductors are
separated, and are ready for mounting in their receivers.
.
The fourth part of my Invention relates to the method of mounting the incan-
descing conductor. For this purpose it is necessary to enlarge the ends of the
same in order to affix the ends of the conducting wires thereto. This has been
done in many ways, by platinum clamps, by depositing metal upon the ends of the
conductor, &c., &c. In any method in which a change of material, as from carbon
to platinum, or any abrupt change in the sectional area of the conductor takes
place, a great difference of temperaturo between neighbouring parts occurs, which
ultimately produces fracture at that point. My improvement consists in forming
these enlargements in one piece with the conductor during the moulding and
compacting process, or subsequently placing them upon the ends of the conductor
by a similar process, the more convenient method for small conductors being the
former, as shown at Figs. 2 & 3. In order to cause all contiguous portions of the
conductor and enlargement to be at but slightly different temperatures, I make the
end of the enlargement take somewhat the form of an acute pyramid, the sides of
which are however curved, Fig. 6.
The fifth part of my Invention relates to the method of supporting the conductor
and attaching the conducting wires. In supporting the incandescing conductor

page_text: with its connections, &c., by means of wires sealed into the material of the receiver
there is liability to fracture of the latter from two causes, 1st, by the conduction
of heat from the incandescing conductor down the metallic wires to the joint; and
2ndly, from the vibration of the conductor (caused by moving or jarring the lamp).
To provide against this it is necessary to make the supporting wires thicker than
is absolutely necessary for the conveyance of the requisite amount of current. My
improvement consists in supporting the incandescing conductor by means of the
carbon enlargements afore mentioned, and shewn in Fig. 6. To do this an auxiliary
stage or diaphragm 8, 8, 8, Fig. 7, is provided. The thermal conductivity of carbon
being low the heat is prevented from roaching the support. From the enlargements
wires pass through the diaphragm, into which they are sealed, and are again sealed
into the material of the receiver by the ordinary (Geissler) method. By thus
supporting the conductor the sectional area of the conducting wire need not be
greater than is absolutely necessary for the passage of the current, and this sectional
area may be made up of several wires instead of one. In addition to the above
mentioned advantages 1 ensure by the use of the diaphragm afore mentioned, and
the method of double sealing, additional safety from leakage. To do this it is
simply necessary to destroy all communication (after the lamp has been evacuated)
between the receiver and the space below the diaphragm. A simple method of
doing this is shown in Fig. 7. The tube t connects the receiver of the lamp with
the space beneath the diaphragm, and projects for a short distance into the
exhausting tube T. When the receiver (and with it the space below the diaphragm.
8, 8, 8,) has been exhausted as far as possible the tube T is heated and sealed off,
and with it the tube t.
The sixth part of my Invention relates to the method of eliminating the
atmospheric air from the receiver. To do this I evacuate the receiver' as far as
possible; then to completely dislodge the atmospheric air I pass through the
receiver a stream of suitable vapour (other than hydro-carbon) or inert gas; I find
the vapour of the bi-sulphide of carbon very suitable and effective; I then re-
exhaust to the highest attainable degree. The apparatus I employ for this purpose
(and which is also applicable to other purposes) is represented in Fig. 8. The
principle of all mercurial pumps (other than that of Sprengel) is that the air
contained in the receivers or vessels to be evacuated is allowed to expand into a
large reservoir, from which it is expelled by filling the large reservoir with
mercury; communication with the atmosphero having been interrupted the mercury
is withdrawn from the said reservoir, producing in the same what is known as the
torricellian vacuum, connection between the said reservoir and the vessels under
exhaustion is re-established, and the air of the latter expands into the former.
This process is repeated until the pump fails to produce a higher degree of
exhaustion, the introduction and withdrawal of the mercury from the reservoir
being effected by connecting to the said reservoir (by means of a flexible tube) a
similar vessel, and raising or lowering the latter above or below the level of the
said reservoir by hand or by a windlass and chain, the pump required constant
attention. There are two great defects in this class of pump. Firstly, on account
of their action being intermittent for during one half of the time no air is being
removed while some is entering by leakage; and, secondly, on account of their
action being sluggish (the efficiency of any exhausting apparatus depending on the
ratio of the amount of air removed to that introduced by leakage); my improve-
ment consists in rendering the action constant and inore rapid. For this purpose I
provide two or two sets of reservoirs, and arrange that while the air is being
expelled from one or one set of reservoirs it is expanding into the other or other
set of reservoirs. A convenient method of doing this is shown in Fig. 8, in
which R, R, representing the reservoirs. In order to force the mercury into
& withdraw it from these I employ either a double acting cylinder and piston or
preferably two cylinders provided with plungers, as in Figs. 8 & 9. The method
of establishing and cutting off communication with the atinosphero has been by
means of stop-cocks, worked by hand or valves actuated by the mercury itself.

page_text: To obviate the use of either the tubes T, T¹, are bent down into a vessel H con-
taining mercury having formed in them at a distance rather greater than the
barometric height of mercury from their open extremity the traps t, t. In order
to prevent any air from returning into the pump it is necessary that a small
quantity of mercury should pass the bends b, b, at each stroke of the pump. To
do this I cause either (1st) the piston or plungers to enter the cylinder a slightly
greater distance at each stroke, or (2nd) an auxiliary plunger to enter the cylinder
a short distance at each stroke, or (3rd) a small quantity of mercury to enter the
cylinder at each stroke. Fig. 9 shows a device for carrying this into effect by the
second method. The small plungers p, p, have a screw thread cut upon part of
their length 8,8', which thread works in the nuts n, n'. Upon the outer extremity
of each plunger are keyed wheels w, wl, having cut upon their edges teeth so
arranged that by the engagement therewith of a pin projecting from the plunger P
a feed is imparted to the small plungers at each stroke. To replenish the cylinder
stop-cocks y, y, (in connection with vessel H) are opened, and x, x¹, (in connection
with the reservoirs) are closed, and upon the plunger being withdrawn mercury
flows from the vessel H into the cylinders; I find the third method however more
effective, as it enables the height of the mercury at h, h', to be kept constant,
which is essential to the proper working of the pump; a method of carrying it
into effect is shown in Fig. 8. The cylinders C, C, are provided with valves V, V'.
During the inward excursion of the plunger the valves are in the position shown
at V, so that the cylinder is in communication with the reservoirs, but during a
portion of the outward excursion of the plunger the valve is moved into the
position V, in which position communication with the reservoirs is cut off and
that with the vessel H established. A quantity of mercury is drawn into the
cylinder dependent upon the time the valve is allowed to remain in this position.
In order to shorten the passage to the vessels to be evacuated a ball valve vis
inserted at the junction of the exhausting tube with the dessicator D, otherwise
the latter would have to be raised above the level of b, b¹, as the mercury would
rise to that height. A convenient way of working the apparatus is to connect the
plunger P by the connecting rod Q to a crank, and to actuate the valves V, VI, by
cams attached to the crank shaft.
The apparatus may very conveniently be worked by a small electro-motor, and
then requires no attention.
Having thus described the nature of my said Invention, and shown the manner
in which the same may be carried into effect, I would have it understood that I
claim,―
First. The manufacture of incandescing conductors for electric lamps from
suitable materials rich in cellulose, by, reducing the same to a finely divided
condition, and moulding the same into the required forms, substantially as
described.
Second. In the manufacture of incandescing conductors for electric lamps, the
method of rendering the material of the same very hard and dense by subjecting it
to great pressure while in a plastic state.
Third. In the manufacture of the incandescing conductors and carbon rods for
electric lamps, the method of rendering the material of the same very imporous and
uniform in its specific electrical resistance by exhausting the air from the same
before and at the time the pressure is applied.
Fourth. In the manufacture of the incandescing conductors and carbon rods for
electric lamps, the method of carbonizing, substantially as set forth.
Fifth. In the manufacture of the incandescing conductors for electric lamps, the
method of forming the enlargements for the attachment of the conducting wires.
Sixth. In the manufacture of the incandescing conductors for electric lamps, the
method of joining and the shape of the junction between the same, and the
enlargements used for the purpose of attaching the conducting wires, substantially
as described and for the purposes specified.
Seventh. In incandescing electric lamps, the method of supporting the incandescing

page_text: conductor by means of the enlargements afore mentioned, substantially as described
and for the purposes specified.
Eighth. In incandescing electric lamps, the use of a diaphragm or stage,
substantially as described and for the purposes specified.
Ninth. In incandescing electric lamps, the method of securing additional safety
from leakage by the use of the diaphragm or stage afore mentioned, substantially
as described.
Tenth. In incandescing electric lamps, the method of eliminating the atmospheric
air from the receiver, substantially as described.
Eleventh. In the exhausting apparatus, the method of rendering the action of
the same continuous by the use of two or two sets of reservoirs, substantially as
described.
Twelfth. In the exhausting apparatus, the method of working the mercury in
the same, substantially as described and for the purposes specified.
In witness whereof, I, the said Alfred Richard Sennett, have hereunto set
my hand and seal, this Fifteenth day of May, in the year of our Lord One
thousand eight hundred and eighty two.