IMPROVEMENTS IN AND CONNECTED WITH INCANDESCENT ELECTRIC LAMPS
Year: 1882

page_text: LETTERS PATENT to George Guillaume André of Dorking in the County of
Surrey for an invention of IMPROVEMENTS IN AND CONNECTED WITH
INCANDESCENT ELECTRIC LAMPS
"
$6
PROVISIONAL SPECIFICATION left by the said George Guillaume André
at the Office of the Commissioners of Patents on the 23rd May 1882.
GEORGE GUILLAUME ANDRÉ of Dorking in the County of Surrey
MENTS IN AND CONNECTED WITH INCANDESCENT ELECTRIC LAMPS
"
"IMPROVE-
In the specification of my patent No 4654 of 1881 I described a mode of
preparing carbon bridges or burners for electric incandescent lamps by filling the
pores of the carbon, or of the yet uncarbonized material, with linseed or other
drying oil, allowing the oil to oxidise, and then carbonising or calcining the material
or the carbon. I now wish to extend this process to the production of burners
mainly from this oxidised oil; I take loose uncompacted vegetable fibre or thread
such as from flax, cotton, hemp, china grass or other similar materials, and immerse
it in boiled linseed oil. Then I remove from it as much of the absorbed oil as I
can by drawing it first between the fingers, and afterwards between blotting paper.
The thread is then exposed to a temperature of about 140° F; till the oil is fully
oxidised. The process is repeated several times till sufficient oil has been taken
up. Or I may first oxidise the oil in thin layers upon sheets of glass or other
suitable material, and having dissolved the oxidised oil in naphtha, dip the thread
in the solution and then allow the solvent to evaporate. In both cases, the vegetable
When
fibre is employed as an absorbent for the oil or a vehicle to carry the oil.
carbonised, the burner prepared in this way is quite different in its physical
qualities from one prepared from thread alone. The former is dense, hard, rigid
and breaks with a short clean fracture, while the latter is soft, loose in texture,
flexible and breaks with a ragged fracture like wood. The former too is of course
much more conductive than the latter.
When a burner for an incandescent lamp is reduced to the dimensions of a mere
filament a small defect in its structure will speedily bring about its destruction.

page_text: I therefore sometimes seek to give to my burners a larger mass of material than
other patentees and manufacturers of incandescent lamps give to theirs, to do this
without lessening the resistance of the burner, I use as the material for the carbon,
the least dense of the suitable materials known to me. Such are willow wood,
particularly withy and the common basket osier, the bark of the osier, and the
bark of the lime tree known in cominerce as "bast." This is not the fibre known
by that name, but the material largely imported into this country from Russia, of
which matting used for packing purposes, and baskets are made.
I may also make a strong and durable burner in the following manner. I take
a thin strip or membrane of vegetable tissue, such as the bast already mentioned
or a thin shaving of withy wood, and having carbonised it I heat it by means of
an electric current in an atmosphere of some hydrocarbon gas at low pressure for
the purpose of slowly depositing upon it graphitoidal carbon. Prepared in this
way, the burner consists mainly of carbon obtained from the hydro carbon gas,
the wood charcoal obtained from the thin strip or membrane being used only for
the purpose of enabling the gas carbon to be deposited.
I have observed that carbon burners, when homogeneous in structure and
properly fixed to the wires in the lamp, usually break in the bent portion of their
length, this being the part which is most strained; a burner may be made more
durable by making the bent portion more conductive than the rest to keep the
temperature lower at that part. As the bent part in such a case will not emit
light, it should be made to be only a small portion of the total length of the burner.
This may be accomplished by making the burner of an inverted V shape, the
highest part being however not bent at an angle, but with a curve of very short
radius. The bent part may be made more conductive than the rest by making
that part thicker, or by coating it with carbon or copper. A burner may be formed
without a bent part by inclining two very slender rods or pencils of carbon till
they meet at their extremities, and then connecting these by a deposit of copper.
I may carbonise the material for the burner in the usual way. But I prefer to
partly carbonise the material under mercury and subsequently to complete the
carbonisation at a high temperature in a muffle or other furnace.
In this case I
place the material to be carbonised bent or otherwise made into the shape required
for the burner, in a vessel containing mercury. The vessel is covered by a lid
provided with a pipe leading into a condensing chamber. Heat is applied to this
vessel, and the temperature of the mercury is slowly raised to the boiling point
which is about 650° F. While passing the boiling point of water, that is from
about 200° to 220° the temperature is made to rise very slowly when the boiling
point of mercury has been reached, the metal begins to distil over rapidly and is
condensed in the condensing chamber. It is kept at the boiling heat for 5 minutes
and then the fire is withdrawn and it is allowed to cool down slowly. The
carbonised material is then removed from the mercury bath and subjected to a
white heat for about 20 minutes in a muffler or other furnace. By carrying out
the first processes of carbonisation I am able to exclude the material wholly from
the action of the air; to apply heat equally and simultaneously to all parts; to
cause it to shrink slowly and equally; to decompose it very slowly and to the same
degree at every point; and to regulate the temperature easily. Instead of mercury
I may use oil, but in that case the oil which will fill the pores of the carbon when
taken out of the bath must be allowed to oxidise before calcining at a high
temperature.
In whatever way I prepare my carbon burners from wood, bark or oil I may
improve their surface by depositing graphitoidal carbon upon same in the manner
described with reference to the thin slip or membrane. In order to obtain readily
the low pressure desired, I make use of a glass tube having an enlargement with
a shoulder at its upper end upon which a stopper may sit. To the lower end is
attached a flexible tube in communication with a vessel containing mercury. By
raising this vessel, the mercury flows up the glass tube till it partly fills the
enlarged upper portion. The burner to be operated upon having been fixed to two

page_text: clamps in the stopper, the latter is put into position to close the upper end of the
tube, the burner being now immersed in the mercury. As the mercury above the
shoulder acts as a seal, a vacuum may be made in the tube by lowering the mercury
vessel. Hydrocarbon gas may then be admitted through a cock in the stopper
and expanded to any required degree. The clamps being in electrical communi-
cation with wires on the outside of the stopper, a current is sent through the
burner, and carbon is deposited upon it. To remove the stopper with the burner
attached the mercury vessel must be again raised.
I may put a liquid hydro carbon upon the mercury in the tube, and in such case
the stopper is sealed by this liquid.
Instead of using this apparatus I may admit hydrocarbon gas into the glass
bulb of the lamp by means of the vacuum apparatus described in the Specification
of my patent No. 4654 of 1881 and deposit the carbon after the burner is mounted.
I may also make the surface of the burner dense and hard by a process of
chilling similar to that adopted for iron and steel. To effect this I heat the burner
by means of an electric current to a bright red heat and then suddenly immerse it
in mercury, this may be done either in the apparatus above described, or in the
lamp bulbs after mounting and while making the vacuum.
Whenever I raise the burner to incandescence for the purpose of depositing carbon
upon it, I prefer to put the current into it gradually. To do this I make use of a
switch containing a connected set of resistances with each of which the handle
makes contact in succession as it is being turned on. Such switches prolong the
life of a carbon burner when adopted for common use.
To avoid the necessity for platinum in the wires at the parts where they pass
through the glass into the bulb I may use hollow copper wires flattened at those
parts. The empty space within the wire allows it to expand without cracking the
glass. I may fix the carbon burner to the wires within the lamp by one of the
methods described in the Specification of my patent No 4654 of 1881 or I may fix
it by soldering or by metallic cements.
For the purpose of connecting the lamp to the bracket chandelier or other
support I have devised a "holder" consisting of a short cylindrical piece of wood,
ebonite or other insulating material, provided with two holes to receive the lamp
wires, and with side springs in communication with the terminals, upon which
springs the wires are pressed and held by an insulating ring slipped over them.
To prevent the wires from being burned in case of an accident and thereby to
avoid the risks from fire and injury to machines I interpose in the circuit a
connection consisting of a piece of lead or other easily fusible wire contained within
a metallic tube and having a terminal screw at each end. The tube retains the
molten metal and serves as complete protection from the flash occasioned by the
break in the circuit.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Guillaume André in the Great Seal Patent Office on the
**23rd November 1882.
GEORGE GUILLAUME ANDRÉ of Dorking in the County of Surrey
MENTS IN AND CONNECTED WITH INCANDESCENT ELECTRIC LAMPS
"
"
IMPROVE-
In the Specification of my Patent No 4654 of 1881 I described a mode of
preparing carbon bridges or burners for electric incandescent lamps by filling the
pores of the carbon or of the yet uncarbonized material with Linseed or other
drying oil allowing the oil to oxidise and then carbonizing or calcining the
material or the carbon, according to my present Invention this process is
applied with improvements to the production of burners in the manner hereinafter
described.
The first part of my Invention consists in the manufacture of a new or improved
carbon bridge or burner I employ vegetable fibre, or thread of a loose absorbent
character, and not containing gummy or other cementing matter, such as fibre from
flax, cotton, hemp china grass or other similar materials and immerse it in boiled
linseed oil. Then I remove from it as much of the absorbed and adhering oil as I
can by drawing it first between the fingers and afterwards between blotting paper.
The thread is then exposed to a temperature of about 140° F till the oil is fully
oxidised; the process is repeated several times till sufficient oil has been taken up.
Or I first oxidise the oil in thin layers upon sheets of glass or other suitable
material and having dissolved the oxidised oil in naphtha dip the fibre or thread
in the solution and thus allow the solvent to evaporate. In both cases the
vegetable fibre is employed as an absorbent for the oil or a vehicle to carry the oil.
When carbonised the burner prepared in this way will be found to be superior for
the purpose intended to the burner made of fibre prepared as described in the
Specification of my said Patent of 1881 although to some extent the same method
of treatment is adopted the fibre or thread prepared according to my present
Invention will be found, to be denser and harder and have the oxidised oil
incorporated more uniformly and better.
I make a burner of an improved form haying the necessary strength at the point
where the thread or fibre is bent or curved by making it of an inverted V shape,
the highest part being however not bent at an angle, but with a curve of very
short radius. The bent part should be made more conductive than the rest by
making that part thicker in the first instance or by coating it with carbon or
copper. A burner may be formed without a bent part by inclining two very
slender rods or pencils of carbon till they meet at their extremities and then
connecting these by a deposit of copper or carbon. Figure 1 of the accompanying
drawings shows such a form of burner. I make my burners short and thick that is
not less than one millimetre in diameter and thus avoid the defects of the so called
filament burners which are long and much smaller in sectional area than mine.
I in some cases carbonise the material for the burner in the usual way but it
will be found more advantageous to partly carbonise the material under mercury.
I in some
cases similarly expose the material to the influence of a fluid by
enclosing it in a box containing air and placed in a bath of mercury "fusible"
metal or sand and subsequently the carbonisation is completed at a high
temperature in a muffle or other furnace. I place the material intended to be
carbonised when it is made in the shape required for the burner in a box a
Figure 2; this box is placed in a vessel b containing mercury. The box a rests on
a piece of earthenware c. The vessel b is covered by a lid provided with a pipe d
leading into a condensing chamber e. Heat is applied to this vessel 6 by
preference by Bunsen burner and the temperature of the mercury is slowly raised
to the boiling point which is about 650° F while passing the boiling point of

page_text: water that is about 200° to 220° F The temperature is made to rise very slowly.
When the boiling point of mercury has been reached the metal begins to distil over
rapidly and is condensed in a condensing chamber or in an open vessel e con-
taining water. It is kept at the boiling heat for five minutes and then the burner
or other fire is withdrawn and it is allowed to cool down slowly. If a sand bath
is used no condensing pipe d and vessel e are needed.
The carbonised material is then removed from the mercury or other bath and
subjected to a white heat for about 20 minutes in a muffle or other furnace. By
carrying out the first process of carbonisation in this manner, I am able in the first
mentioned case wherein I carbonise under mercury to exclude the material wholly
from the air and in both cases mentioned the heat being applied through the
medium of a fluid I am able to apply the heat equally and simultaneously to all
parts to cause it to shrink slowly and equally to decompose it very slowly and to
the same degree at every point and to regulate the temperature easily.
I in some cases improve the surface of my carbon burners by depositing
graphitoidal carbon upon same from some hydro-carbon gas or vapour. I also
make the surface of incandescent carbon burners dense and hard by a process of
chilling similar to that adopted for iron and steel. To effect this I beat the burner
by means of an electric current to a bright red heat then suddenly immerse it in
mercury this may be done in the lamp bulbs after mounting and while making the
vacuum by Torricellis method. Or instead of mercury I may use mineral oil.
Whenever I raise the burner to incandescence for the purpose of depositing
carbon upon it I find it advantageous to put the current into it gradually. To do
this I make use of a switch containing a connected set of resistances with each of
which the handle makes contact in succession as it is being turned on. Such
switches also prolong the life of a carbon burner if they are adopted in connection
with the lamp itself when in use.
For the purpose of connecting the lamp to the bracket chandelier or other
support I have devised a holder. Figure 3 is a sectional view of this holder con-
sisting of a short cylindrical piece d of wood ebonite, or other insulating material
provided with two holes a' to receive the lamp wires band with side springs c in
communication with the terminals upon which springs the wires are pressed, and
held by an insulating ring d' slipped over then.
Having now described the nature of my said Invention and in what manner
the same is to be performed I declare that I claim :—
First. The improved method of treating fibres or threads so as to properly
impregnate them with oxidised oil and produce a burner or burners of an improved
character substantially as above described.
Second-The form and construction of burner as described and shown at
Figure 1 consisting of two straight parts or halves which converge to a very short
and thicker bend or angle.
Third. The special modes of carbonizing incandescent burners by treating the
material by the employment of mercury substantially as herein described.
Fourth. The manufacture of burners with an improved carbon surface by
dipping them while hot in a mercury or mineral oil bath substantially as
described.
Fifth. The construction of lamp holder described and shewn at Figure 3.
In witness whereof I the said George Guillaume André have hereunto set
my hand and seal this Twentythird day of November in the year of Our
Lord One thousand eight hundred and eighty two.