IMPROVEMENTS IN THE MANUFACTURE OF ELECTRODES FOR ELECTRIC LIGHTING, AND IN THE MANNER OF PARTIALLY PROTECTING THE INCANDESCENT POINTS FROM OXIDISING OR DESTRUCTIVE ACTION
Year: 1878

page_text: LETTERS PATENT to Archibald Henry Plantagenet Stuart-Wortley, of Rosslyn
House, Grove End Road, London, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF ELECTRODES FOR ELECTRIC LIGHTING, AND IN THE MANNER
OF PARTIALLY PROTECTING THE INCANDESCENT POINTS FROM OXIDISING OR
DESTRUCTIVE ACTION."
Sealed the 14th March 1879, and dated the 17th September 1878.
PROVISIONAL SPECIFICATION left by the said Archibald Henry Plantagenet
Stuart-Wortley at the Office of the Commissioners of Patents on the 17th
September 1878.
"
ARCHIBALD HENRY PLANTAGENET STUART-WORTLEY, of Rosslyn House, Grove
End Road, London. IMPROVEMENTS IN THE MANUFACTURE OF ELECTRODES FOR
ELECTRIC LIGHTING, AND IN THE MANNER OF PARTIALLY PROTECTING THE
INCANDESCENT POINTS FROM OXIDISING OR DESTRUCTIVE ACTION."
This Invention of improvements in the manufacture of electrodes for electric
lighting, and in the manner of partially protecting the incandescent points from
oxidising or destructive action consists in making the electrodes or carbon sticks of
certain mixtures of carbon and highly refractory materials, and in protecting the
points with a thin coating of some highly refractory material as a means of retarding
the burning away and consequent rapid waste of the carbon sticks of an ordinary
electric regulator or lamp during the production of the electric light.
It is well known that during the production of such a light the incandescent
points of the carbons forming the electrodes are gradually burned away by the
formation of some gas or gases due to the combination of the incandescent carbon
with some gas or gases contained in the atmosphere, or by some other chemical or
electric action.
The object of my Invention is to provide the carbon points with some covering
which, whilst permeable to the électric arc, shall be of such a nature as to render

page_text: the approach of gases atmospheric or otherwise to the incandescent points a matter
of difficulty, but which shall nevertheless freely permit the passage of the
electric arc.
My first method consists in covering each of the carbon points with a hood or
cap of some material which is highly heat resisting, and at the same time of
such a texture as to be pervious to the electric arc, either between its neighbouring
particles or between the meshes of its texture when I give it that form. The
substance I use by preference is asbestos (a silicate of magnesia), though similarly
highly refractory materials will probably answer the purpose. The asbestos is spun
and woven into a cap or hood, and is placed over the carbon points, or the lower
point may have a ring or ferrule of the asbestos or other heat-resisting fabric
projecting slightly above the end of the point, with the object of containing the
finely powdered asbestos or of some other heat-resisting material in a thin stratum
on the top of the carbon point.
My second method consists in modifying the manufacture of the carbon points or
sticks by the admixture of a certain quantity of some highly heat-resisting substance,
preferably asbestos, with the gas coke previously to its being formed into sticks and
baked. When the carbon sticks so made are used as the electrodes of the electric
lamp, I find that during the first few moments, the superficial carbon from the tips
is burned away, but that the heat-resisting material remaining as a thin covering on
the incandescent points checks the further approach of atmospheric air, and thus
the burning away of the points is retarded. The proportions of the resisting
material to the carbon vary with the quality of the materials and strength of
current used.
In the employment of either of these methods in the event of the electric circuit
being interrupted and the light going out, it may happen on the re-approach of the
carbons by the mechanical regulator of the lamp that the heat-resisting covering
will insulate the points and prevent the re-establishment of the circuit and light.
To prevent this I prefer to place the carbons somewhat obliquely one to the other,
so that when one carbon touches upon the other a slight kind of shearing action
takes places, which causes the superficial covering of heat-resisting material to be
rubbed off, and allows the carbon particles to come together and to re-establish the
circuit and the light.
In order to prevent the heat-resisting covering from facilitating the formation of
the electric arc at the back of the carbon points, so that a large proportion of the
light might be lost in the shadow of the carbons themselves, I prefer to cause the
electric arc to take up a steady position in the front of the carbon point by means
of a magnet suitably placed in the neighbourhood of the light, and which causes
the elecric arc to be deflected or bent outwards in one determined direction.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Archibald Henry Plantagenet Stuart-Wortley in the Great Seal Patent
Office on the 17th March 1879.
ARCHIBALD HENRY PLANTAGENET STUART-WORTLEY, of Rosslyn House, Grove
End Road, London. "IMPROVEMENTS IN THE MANUFACTURE OF ELECTRODES FOR
ELECTRIC LIGHTING, AND IN THE MANNER OF PARTIALLY PROTECTING THE
INCANDESCENT POINTS FROM OXIDIZING OR DESTRUCTIVE ACTION."
This Invention of improvements in the manufacture of electrodes for electric
lighting, and in the manner of partially protecting the incandescent points from
oxidizing or destructive action relates to the manufacture of the electrodes or carbon
sticks by using certain mixtures of carbon and highly refractory materials; also
protecting the points with a thin coating or covering of some highly refractory
material, in each case as a means of retarding the burning away and consequent
rapid waste of the carbon sticks of an ordinary electric regulator or lamp during
the production of the electric light.
It is well known that during the production of such a light the incandescent
points of the carbons forming the electrodes are gradually burned away by the
formation of some gas or gases due to the combination of the incandescent carbon
with some gas or gases contained in the atmosphere, or by some other chemical or
electric action.
The object of my Invention is to provide the carbon points with some covering
which, whilst permeable to the electric arc, shall be of such a nature as to render
the approach of gases atmospheric or otherwise to the incandescent points a
matter of difficulty, but which shall nevertheless freely permit the passage of the
electric arc.
My first method consists in covering each of the carbon points with a hood or cap
of some material which is highly heat resisting, and at the same time of such a
texture as to be pervious to the electric arc, either between its neighbouring particles
or between the meshes of its texture when I give it that form. The substance I
use by preference is asbestos (a silicate of magnesia), though similarly highly refrac-
tory materials will probably answer the purpose. The asbestos is spun and woven
into a cap or hood, and is placed over the carbon points, or the lower point may
have a ring or ferrule of the asbestos or other heat-resisting fabric projecting
slightly above the end of the point with the object of containing the finely-
powdered asbestos or of some other heat-resisting material in a thin stratum on the
top of the carbon point.
My second method consists in modifying the manufacture of the carbon points or
sticks by the admixture of a certain quantity of some hightly heat-resisting sub-
stance, preferably asbestos, with the gas coke previously to its being formed into
sticks and baked. When the carbon sticks so made are used as the electrodes of the
electric lamp, I find that during the first few moments the superficial carbon from
the tips is burned away, but that the heat-resisting material remaining as a thin
covering on the incandescent points checks the further approach of atmospheric air,
and thus the burning away of the points is retarded. The proportions of the
resisting material to the carbon vary with the quality of the materials and strength
of the current used.
In the employment of either of these methods in the event of the electric circuit
being interrupted and the light going out, it may happen on the re-approach of the
carbons by the mechanical regulator of the lamp that the heat-resisting covering
will insulate the points and prevent the re-establishment of the circuit and light.
To prevent this I prefer to place the carbons somewhat obliquely one to the other,
so that when one carbon touches upon the other a slight kind of shearing action
takes place, which causes the superficial covering of heat-resisting material to be

page_text: rubbed off, and allows the carbon particles to come together and so re-establish the
circuit and the light.
In order to prevent the heat-resisting covering from facilitating the formation of
the electric arc at the back of the carbon points, so that a large proportion of the
light might be lost in the shadow of the carbons themselves, I prefer to cause the
electric arc to take up a steady position in the front of the carbon points by means
of a magnet suitably placed in the neighbourhood of the light, and which causes
the electric arc to be deflected or bent outwards in one determined direction, but I
do not claim this directing of the arc as part of my Invention.
As to the second method I have found that the use of the silicate of magnesia is
greatly dependent on the relative conductivity of the samples used, and I find very
good results from the use of steatite as combined in the following mixture:-
Carbon of gas retorts
-
10 parts
(steatite 1)
The use of the plumbago is indicated to obviate certain difficulties as to the
conductivity of different samples of steatite, as above mentioned; sufficiently good
conducting samples of steatite do not require the plumbago.
I find the first method described in my Provisional Specification of using the
silicate of magnesia (asbestos) either in the form of a loose cap, or mixed with the
materials, is not so effective as the electrodes of the kind of composition above
described.
The process of combining the materials used and thereby forming the electrodes
is substantially similar to those in ordinary use; the composition is ground and
mixed by suitable machinery, and pressed into moulds and drawn through dies in
the usual manner.
I am aware that many attempts have been made to improve the quality of the
light by mixing various substances with the carbons for the electrodes, but in no
case that I am aware of has any other person suggested the use of any of the silicates
of magnesia for the purpose of protecting and preventing the too rapid burning
away of the electrodes, and for giving, as I have ascertained, greatly increased
steadiness to the light. I have ascertained the value of the electrodes thus composed
of a portion of silicate of magnesia as described in protecting the electrodes from
too rapid waste, and although the conductivity of the electrodes is slightly impaired
by the varying conductivity of the samples of silicate of magnesia, I have found it
to be essentially and practically restored by varying the kind of carbon used,
namely, by letting a portion of the carbon used be in the form of plumbago, as I
have above set forth.
Having now described and particularly set forth the nature of the Invention, and
the manner of carrying the same into effect, I would have it understood that what
I claim and desire to secure in the herein-before in part recited Letters Patent is,―
First. The respective combination of parts contained in my improved electrodes
respectively, substantially as described.
Second. The use of silicate of magnesia for the purposes described.
In witness whereof, I, the said Archibald Henry Plantagenet Stuart-Wortley,
have hereunto set my hand and seal, this Fourteenth day of March, in the
year of our Lord One thousand eight hundred and seventy-nine.