IMPROVEMENTS IN AND CONNECTED WITH PRODUCING LIGHT BY ELECTRICITY
Year: 1878

page_text: LETTERS PATENT to Isac Louis Pulvermacher, of 194, Regent Street, in the
County of Middlesex, Electrician, for the Invention of "IMPROVEMENTS IN
AND CONNECTED WITH PRODUCING LIGHT BY ELECTRICITY."
Sealed the 20th May 1879, and dated the 23rd November 1878.
PROVISIONAL SPECIFICATION left by the said Isac Louis Pulvermacher at
the Office of the Commissioners of Patents on the 23rd November 1878.
ISAC LOUIS PULVERMACHER, of 194, Regent Street, in the County of Middlesex,
Electrician. "IMPROVEMENTS IN AND CONNECTED WITH PRODUCING LIGHT BY
ELECTRICITY."
My improvements relate to various apparatus for the production of electric light,
varying according to the method employed, either lighting by the voltaic arc or by
incandescence.
For lighting by the voltaic are, the principal organ or medium I employ is com-
posed of two parts invariably connected together which I term "rod-spiral."
The central portion of this rod consists of a thinner rod composed of a paste or
compound of fine powdered pure charcoal mixed with tar and pitch, and obtained
by pressure through a draw plate.
The surrounding or enveloping part consists of a thinner carbon rod or thread
also obtained by pressure through a draw plate.
This thin rod is provided in the course of manufacture with a central textile
thread forming a kind of core, and giving cohesion and strength to the carbon.
The said enveloping or surrounding rod in a malleable state, and provided with
its interior textile thread, is wound in spiral coils around the central rod, leaving
about one millimetre between the coils, so that they do not touch each other.
The central rod should be previously coated with an insulating and refractory
material, as, for example, plaster, mica, asbestos, and the interstices formed by the
separation of the coil may also be filled by an insulating and refractory material.

page_text: The "rod-spiral" thus obtained by means of a central rod forming the core, and
of an envelloping or surrounding rod wound in spirals, is placed in a box filled with
powdered or pulverized carbon or other suitable material for the baking operation.
I thus obtain "rod-spirals" of indefinite length according to the size of the apparatus
to which they are applied, and having remarkable solidity resulting from the com-
bination and the adherence of the central rod with the spirals around it.
This "rod-spiral" is placed on a very simple apparatus composed of two metal
tubes diametrically separated by a glass tube or other insulating material.
The end of the central rod of carbon extends beyond the last twist or coil of the
spiral, and is enclosed by a small metal cap which fits tight in the internal metal
tube, whilst the exterior diameter of the spiral carbon is in contact with the interior.
of the external metal tube which is higher than the glass tube.
The apparatus being thus fixed, surmounted by the "rod-spirals," it will only be
necessary to put each of the tubes in contact with one of the poles of any battery or
electro generator to obtain an electric light by the voltaic arc, the seat of which
will be at the upper end of the "rod-spirals" between the central carbon rod and
the extreme end of the carbon spiral which need only to be conductibly connected
temporarily for establishing the arc.
The carbon rod by reason of the combustion will burn vertically, and the spiral
will burn circularly around the rod nearly horizontally, according to the inclination
given to the twists of the spiral.
The combustion of the carbon being rather rapid, it may be understood that the
arrangement of a fixed spiral around a central rod forming a core relatively much
thicker than the body of the spiral has considerable importance relative to the
duration of the "rod-spiral," since this spiral has a length much greater than a
straight rod by reason of its windings or twists.
As I have already stated, my "rod-spirals" may be long or relatively short
according as they are to last for a greater or less length of time, and I may also
arrange apparatus for causing the said "rod-spirals" to ascend progressively to
keep the light at a fixed and uniform height, for which purpose I may employ the
following arrangement :-
The central hollow rod of the "rod-spiral" furnished with a capsule pierced with
a hole and surrounded by the carbon spiral rests in a kind of basin or receiver
terminating downwards in a ferrule which slides in a metal tube touching its
sides. This tube forms the upper part of the apparatus, and may be the head of a
public or street lamp.
The basin and its ferrule are fastened with thin cords passing over pullies, and to
which a counter weight is suspended. The "rod-spiral" has consequently a constant
tendency to rise in proportion as its combustion takes place to maintain a regular
position at the seat of the light, but in order that it shall not mount quicker than
is desired, the central rod of the "rod-spiral" is provided with a hole or hollow
centre extending its whole length formed during the process of manufacture. A
metal tube passes through this hollow centre; its lower end is fastened in the base
of the supporting apparatus.
Its upper end is terminated by an inverted conical refractory disc, which being
larger than the orifice of the hollow centre stops the "rod-spiral," thus preventing
the too rapid motion imparted to it by the descent of the counterweight.
A metal conducting wire is employed wound in spiral coils capable of developing
a sufficient length to keep pace with the motion of the "rod-spiral." This wire, to
which is attached a conducting wire of an electro-generator, is fastened at one end
to the carbon rod cap, thereby transmitting the current to it, and its other end is
fastened to a disc or washer of insulating material fixed in the external tube.
The conducting wire of the other pole communicates the current first to the
external tube, then to an annular spring pressing gently near the upper end of the
carbon "rod-spiral."
I have also devised a practical means to light and to instantaneously re-light in
case of extinction from any cause. For this purpose I pass through the metallic

page_text: centre tube a metallic rod which passes freely through the centre of the cone, and
may be turned by taking hold of its lower end.
At its upper end it is terminated by a kind of small metallic brush inclined
downwards, whose temporary contact with the carbon rod and the end of the spiral
is sufficient to light by its temporarily closing the circuit.
The reverse movement of the rod suffices to interrupt the contact of the brush
with the end of the spiral for the establishment of luminous arc and production of
the light.
In the "rod-spirals" hitherto described I have referred to the central rod as
being surrounded with one spiral only, but I may also surround the central rod
with two, three, or more spirals after the manner of double or treble threaded
screws, the upper ends of which will burn simultaneously and circularly around.
and with the central rod, and by giving simultaneously as many arcs as there are
spirals, will thus obviate any shadows.
In the second case, that is, for lighting by incandescence, I may adopt several
arrangements, the first of which consists in inserting in the circuit a vast number
of very thin platinum wires at a very little distance from each other, and in such a
manner that they represent a bundle of wires, nearly similar to a brush, composed
of a number of platinum loops the two ends of which are set in a permanently good
contact with a good conducting medium.
One method of carrying this part of my Invention into effect is as follows:-
Loops are formed in a practical manner by winding a thin platinum wire over
two wires of good conduction and of larger diameter, kept apart at the distance of
half the length that it is intended to give to the loops. By this means a sort of
band of a certain width is formed in an analogous manner to my galvanic bands.
I then solder the edges of the platinum bands to the stouter conducting wires which
they surround. The band may then be used in this state or folded longitudinally
so as to bring the two edges of the band parallel to each other, thus forming loops
of the platinum wires.
In the fold or groove thus formed a strip of mica or other suitable insulating
substance is laid for preventing contact between one edge of the band and the other
when one of the conducting wires is brought in contact at one of its ends with one
pole of an electro generator, and the other conducting wire has one of its ends in
connection with the other pole, the current can only pass by circulating through all
the very thin platinum wires above referred to, which thereby become incandescent
to a white heat, and consequently luminous.
It is well understood that the quantity of electricity to be brought into play is
to be graduated and adjusted in proportion to the number of such platinum wires
forming the luminous volume or mass, in order, on the one hand, that no fusion of
the platinum wire can take place, and, on the other hand, that the total resistance
in the external circuit created by the insertion therein of all the platinum loops
should approximate to the internal resistance in the electro generator.
In order to concentrate the whole into a small bulk and compact form, I roll it
either into a circular convoluted or spiral form, when it has the approximate
appearance of a brush, in which state it may be inserted in a glass or other trans-
parent enclosure to prevent the cooling of the incandescent platinum loops by the
current of air which their heat produces when unenclosed. By this means no
waste of heat can take place, and consequently the full intensity of the light is
conserved.
I may also form a vast number of platinum loops soldered to conducting wires in
the following manner :-
Through holes formed in a plate or strip of mica, or any other suitable material,
I pass thin platinum wires, so as to form loops of the lengths intended.
The under portions of the platinum wires are set in united conduction with a
thicker wire which is provided during manufacture.
The number of such rows of loops are then brought in connection in alternate
order, one half with one pole and the other half with the other pole of the electro

page_text: generator; that is to say, supposing there are 12 rows, the six even numbers will be
in connection by one conducting wire with one pole of the electro generator, and
the six odd numbers by another conducting wire in connection with the other
pole..
The circuit thus established will cause the current to be distributed to the
number of platinum wire loops, and render them incandescent in a similar manner
to that described above.
I sometimes coat or surround the loops with platinum black, with or without a
mixture of powdered asbestos or similar substance.
A further modification of the above consists in the use of platinum foil in lieu of
the thin platinum wire, to be made incandescent to a white heat by the electric
current, whereby the degree of heat causing fusion has no injurious effect.
I affix such platinum foil on a thin plate of mica or other suitable insulating
material capable of resisting heat, by a suitable adhesive heat resisting compound,
for instance, silicate of potash. I provide the two edges with elongated clamps
capable of good conduction, and pressing on the whole edge surface of the platinum
foil, which clamps are in connection with the poles of the electro generator. The
current supplied to these clamps must traverse the platinum foil, thereby making it
incandescent to a white heat in a similar way to that described above for the
platinum wire.
The platinum being supported by its backing will not easily become disarranged,
and will secure a lasting luminous sheet so long as a current of sufficient intensity
passes.
The shape and size of such illuminating plates depend upon the particular purpose
for which the light is intended.
A thin platinum coating on the insulating and refractory material may also be
secured if preferred by a chemical process.
In the above described method of producing light the current is constantly con-
tinuous, but if it is intended to produce the luminous phenomena by multitudes of
sparks produced by an intermittent current, I use these kinds of brushes as
electrodes, one of them being caused to rotate by a small magnetic engine, thereby
rubbing on the surface of the other electrode, which is in a fixed position beneath.
In this case the loops need only to be short and the platinum wire hard drawn,
and disseminated so far apart as would secure regular and distinct interruptions
by the rubbing of one electrode over the surface of the other.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Isac Louis Pulvermacher in the Great Seal Patent Office on the
23rd May 1879.
ISAC LOUIS PULVERMACHER, of 194, Regent Street, in the County of Middlesex,
Electrician. "IMPROVEMENTS IN AND CONNECTED WITH PRODUCING LIGHT BY
ELECTRICITY."
My improvements relate to various apparatus for the production of electric light
varying according to the method employed, either lighting by the voltaic arc, or by
incandescence.
For lighting by the voltaic arc the principal organ or medium I employ is
composed of two parts, invariably connected together, which I term "rod-spiral."
The central portion of this rod consists of a thinner rod composed of a paste or
compound of fine powdered pure charcoal mixed with tar and pitch or by com-
pression of lamp black, and obtained by pressure through a draw plate.
The surrounding or envelloping part consists of a thinner carbon rod or thread,
also obtained by pressure through a draw plate. This thin rod is provided in the
course of manufacture with a central textile thread forming a kind of core, and
giving strength to the carbon.
The said envelloping or surrounding rod in a malleable state and provided with
its interior textile thread is wound in spiral coils around the central rod, leaving
about one millimetre between the coils, so that they do not touch each other.
The central rod should be previously coated with an insulating and refractory
material, as, for example, plaster, mica, asbestos, and the interstices formed by the
separation of the coils may also be filled by an insulating and refractory material.
The "rod spiral" thus obtained by means of a central rod forming the core, and
of an envelloping or surrounding rod wound in spirals, is placed in a box filled with
powdered or pulverized carbon, or other suitable material for the baking operation.
I thus obtain "rod-spirals" of indefinite length according to the size of the
apparatus to which they are applied, and having remarkable solidity, resulting from
the combination and the adherence of the central rod with the spirals around it.
And in order to enable my Invention to be more fully understood, I proceed to
describe it with reference to the annexed Drawings.
The "rod spiral" is placed, as seen in Figure 1, on a very simple apparatus
composed of two metal tubes a, b, diametrically separated by a tube c of glass or
other insulating material.
The end of the central rod of carbon d extends beyond the last twist or coil of
the spiral fand is enclosed by a small metal cap e which fits tight in the internal
metal tube a whilst the exterior diameter of the spiral carbon fis in contact with
the interior of the external metal tube b which is higher than the glass tube. The
apparatus being thus fixed surmounted by the "rod spiral" it will only be necessary
to put each of the tubes a, b, in contact with one of the poles of any battery or
electro-generator to obtain an electric light by the voltaic arc, the seat of which will
be at the upper end of the "rod-spiral" between the central carbon rod d and the
extreme end of the carbon spiral f, which need only to be conductibly connected
temporarily for establishing the arc.
The central carbon rod d by reason of the combustion will burn nearly vertically
and the spiral will burn circularly around the rod d nearly horizontally according
to the inclination given to the twists of the spiral.
The combustion of the carbon being rather rapid it may be understood that the
arrangement of a fixed spiral around a central rod forming a core relatively much
thicker than the body of the spiral has considerable importance relative to the
duration of the "rod-spiral" since this spiral has a length much greater than a
straight rod by reason of its windings or twists.
As I have already stated my "rod-spirals" may be long or relatively short, ac-
cording as they are to last for a greater or less length of time, and I may also

page_text: arrange apparatus for causing the said "rod-spirals" to ascend progressively to keep
the light at a fixed and uniform height, for which purpose I may employ the arrange-
ment seen in vertical section in Figure 2.
The central rod d' of the "rod-spiral" (which in this case is hollow) is furnished
with a cap el pierced with a hole and surrounded by the carbon spiral f¹. This
latter rests in a kind of basin or receiver g terminating downwards in a ferrule h
which slides in a metal tube i touching its sides with slight friction. This tube
forms the upper part of the apparatus and may be the head of a public or street lamp
post.
The basing and its ferrule h are fastened with thin cords ; passing over pullies
, to each of which cords a counter weight k is suspended.
The "rod-spiral" has consequently a constant tendency to rise in proportion as
its combustion takes place to maintain a regular position at the seat of the light.
But, in order that it shall not mount beyond a given point, the central rod d' of
the "rod-spiral" is provided with a hole or hollow centre extending its whole
length, formed during the process of manufacture. A metal tube m passes through
this hollow centre, its lower end being fastened in the base of the supporting
apparatus. Its upper end is terminated by an inverted conical stop n, which being
larger than the orifice of the hollow centre stops the "rod spiral," thus preventing
the too rapid motion imparted to it by the descent of the counterweight k.
"
A metal conducting wire o is employed wound in spiral coils, capable of de-
veloping a sufficient length to maintain the conduction in spite of the motion of the
rod-spiral." This wire, to which is attached a conducting wire p of any electro-
generator, is fastened at one end to the carbon rod cap el or to the metal rod y,
thereby transmitting the current to it, and its other end is fastened to a disc or
washer of insulating material q fixed in the external tube i.
The conducting wire 7 of the other pole communicates the current first to the
external tube i, then to the ferrule h, and through this to the external carbon f'.
I have also devised a practical means to light and to instantaneously re-light in case
of extinction from any cause. For this purpose I pass through the metallic centre
tube m a metallic rod y which passes freely through the centre of the cone n and
may be turned by taking hold of its lower end. At its upper end it is terminated
by a kind of small metallic brush inclined downwards, whose temporary contact
with the carbon rod d' and the end of the spiral f' is sufficient to light by its tem-
porarily closing the circuit.
The reverse movement of the rod y suffices to interrupt the contact of the brush
with the end of the spiral for the formation of luminous arc and production of the
light.
In the "rod-spirals "hitherto described I have referred to the central rod as being
surrounded with one spiral only, but I may also surround the central rod with two,
three, or more spirals after the manner of double or treble threaded screws, the
upper ends of which will burn simultaneously and circularly around and with the
central rod, and by giving simultaneously as many arcs as there are spirals will thus
obviate any sharp shadows.
Another method I have adopted for re-lighting is shown in Figure 2°. In this
case the stopper n is provided with a number of very fine holes n¹ bored in a
direction at a right angle to the vertical axis or slantingly downwards, and the
central metallic tube m supplies it with ordinary gas, after the manner of a Bunsen
burner, in order to produce small jets of flame without smoke, the said jets serving
as a conductor enabling the arc to establish itself between the carbon spiral and the
top of the carbon cylinder.
The jets are to be kept constantly burning so as to be always ready to light
whenever the circuit is complete.
In the second case, that is, for lighting by incandescence, I adopt several arrange-
ments, the first of which consists in inserting in the circuit a vast number of very
thin platinum wires at a very little distance from each other, and in such a manner
that they represent a bundle of wires nearly similar to a brush composed of a

page_text: number of platinum loops, the two ends of which are set in a permanently good
contact with a good conducting medium.
One method of carrying this part of my Invention into effect is shown in Figure 3.
Loops are formed in a practical manner by winding a thin platinum wire over two
wires of good conduction and of larger diameter, kept apart at the distance of half
the length that it is intended to give to the loops. By this means a sort of band
of a certain width is formed in an analogous manner to my galvanic bands. I then
solder the edges of the platinum band to the stouter conducting wires which they
surround. The band may then be used in this state or folded longitudinally so as.
to bring the two edges of the band parallel to each other, thus forming loops of the
platinum wires. In the fold or groove thus formed a strip of mica or other suitable
insulating substance is laid for preventing contact between one edge of the band
and the other.
When one of the conducting wires is brought in contact at one of its ends with
one pole of an electro-generator, and the other conducting wire has one of its ends
in connection with the other pole, the current can only pass by circulating through
all the very thin platinum wires above referred to, which thereby become incan-
descent to a white heat, and consequently luminous.
In order to concentrate the whole into a small bulk and compact form I roll it
either into a circular, convoluted, or spiral form, when it has the approximate
appearance of a brush, in which state it may be inserted in a glass or other trans-
parent enclosure to prevent the cooling of the incandescent platinum loops by the
current of air which their heat produces when unenclosed. By this means no
waste of heat can take place, and consequently the full intensity of the light is
conserved.
I may also form a vast number of platinum loops soldered to conducting wires
in the manner shown in Figures 3 and 4. Through holes formed in a plate or
strip of mica p, or any other suitable material, I pass thin platinum wires q so as to
form loops of the lengths intended.
The under portions of the platinum wires are set in united conduction with a
thicker wire r, which is provided during manufacture. The number of such rows
of loops are then brought in connection in alternate order, one half with one pole, and
the other half with the other pole of the electro-generator, that is to say, supposing
there are 12 rows; the six even numbers will be in connection by one conducting wire
with one pole of the electro-generator, and the six odd numbers by another con-
ducting wire in connection with the other pole. The circuit thus established will
cause the current to be distributed to the number of platinum wire loops and render
them incandescent in a similar manner to that described above.
I sometimes coat or surround the loops with platinum black, with or without a
mixture of powdered asbestos or similar substance.
A further modification of the above consists in the use of platinum foil in lieu of
the thin platinum wire, to be made incandescent to a white heat by the electric
current, whereby the degree of heat causing fusion has no injurious effect. I affix
such platinum foil on a thin plate of mica or other suitable insulating material
capable of resisting heat by a suitable adhesive heat-resisting compound; for
instance, silicate of potash. I provide the two edges with elongated clamps capable
of good conduction, and pressing on the whole edge surfaco of the platinum foil,
which clamps are in connection with the poles of the electro-generator. The current
supplied to these clamps must traverse the platinum foil, thereby making it incan-
descent to a white heat in a similar way to that 'described above for the platinum
wire.
The platinum being supported by its backing will not easily become disarranged,
and will secure a lasting luminous sheet so long as a current of sufficient intensity
passes. The shape and size of such illuminating surfaces depend upon the particular
purpose for which the light is intended. A thin platinum coating on the insulating
and refractory material may be obtained, if preferred, by a chemical process, and
incrusted or solidified by baking process.

page_text: One method of practically carrying out this part of my Invention is seen in
Figure 5. a is a bell or cone shaped cylinder of hard glass, porcelain (or other
similar refractory material having a glazed surface) metallized by platinum, as
above described. This bell or cylinder is provided at its top b with a hole to enable
it to take over a central metallic rod or stem c, and to rest upon a washer either
soldered to or forming part of the central rod. The upper portion of this central
rod is screw threaded, so that the cone or cylinder can be held secure by means of
the nut d and dished washers.
The lower end of the cone or cylinder is embraced and held by an annular ledge
or gutter e, which in its turn rests upon and is supported by the rod f, which secures
perfect conduction.
One pole of the electro-generator is in connection with the central rod c, and the
other pole with the rod f. The electricity being able to pass only through the
incrusted platinum renders it incandescent to a white heat without danger of the
platinum being fused.
The platinized surface, instead of being of bell or cone shape, may be spherical
or of any suitable shape.
And 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. I claim the "rod-spiral" candle hereinbefore described and substantially
as shown in Figure 1.
Secondly. The modified and improved "rod-spiral" candle shown in Figure 2,
the seat of whose light is kept at a fixed point by the stopper counterbalancing the
action of the weights, the said stopper allowing a rod in its centre to move a brush
held by it for momentarily closing the circuit in lieu of the conducting fuses hitherto
employed.
Thirdly. The modification of Figure 2, shown in Figure 2ª, in which the circuit
is completed and the lighting obtained by means of small jets of gas supplied through
the tube and the holes in the stopper, as herein before described.
Fourthly. The methods of lighting by incandescence, as herein before described,
and as shown respectively in Figures 3, 3, 4, and 5
In witness whereof, I, the said Isac Louis Pulvermacher, have hereunto set
my hand and seal, this Twenty second day of May, One thousand eight
hundred and seventy nine.