IMPROVEMENT IN MEANS FOR DEVELOPING MAGNETISM AND ELECTRIC CURRENTS, AND IN Apparatus FOR ILLUMINATING BY ELECTRICITY
Year: 1878

page_text: LETTERS PATENT to Thomas Alva Edison, of Menlo Park, in the State of
New Jersey, United States of America, for the Invention of "IMPROVEMENT
IN MEANS FOR DEVELOPING MAGNETISM AND ELECTRIC CURRENTS, AND IN
Apparatus FOR ILLUMINATING BY ELECTRICITY."
Sealed the 28th February 1879, and dated the 28th December 1878.
PROVISIONAL SPECIFICATION left by the said Thomas Alva Edison at the
Office of the Commissioners of Patents on the 28th December 1878.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENT IN MEANS FOR DEVELOPING MAGNETISM AND
ELECTRIC CURRENTS, AND IN APPARATUS FOR ILLUMINATING BY ELECTRICITY."
The first part of my Invention relates to a dynamo-magneto-electric machine.
In machines of this class olectric currents have been developed in helices, and a
portion of the current has been taken through the helices of the field of force
magnets, and other portions have been employed in electric lights and for other
uses.
In these machines the currents that pass through the field of force magnets are
expended simply in developing magnetism. I have discovered a method of
developing magnetism, and increasing the same to the maximum point according to
the power employed in rotating the parts, without the use of helices around the
field of force magnets; hence the electric current that is developed in the magneto
electric machine can be entirely employed for lighting and other uses outside of the
machine, instead of a portion being used to develop magnetisın.
When a piece of steel is brought within the magnetic field of a permanent
magnet the same becomes a magnet. I arrange a machine so that the induced
nagnetism re-acts upon the permanent magnet to increase its power, and thus
develop magnetism by mechanical force in a manner somewhat similar to the develop-
ment of electricity in a magneto electric machine.

page_text: One of the devices I have employed consists of a shaft having radial bars, which
is revolved with the ends of the bars as near as possible to the poles of permanent
magnets, and the other poles of the magnets being adjacent to the hub or near the
other ends of the bars. In their revolution the bars become magnetized, and
increase the magnetism in the permanent magnets until the maximum magnetism
is developed.
These magnets are employed as field of force magnets in the magneto electric
machine.
The development of a continuous current of electricity is also desirable, for.which
purpose I employ copper rings or segments around an iron core, and I use mechanical
revolution, whereby the electric action, developed upon the general principle of the
copper disc between two magnetic poles, as experimented upon by Arago, is con-
verted into a continuously flowing electric current.
I make use of an electric candle composed of a strip of platina or similar metal
that withstands a high temperature. The same is made by rolling out flat a strip
that is thicker at one edge than the other, and at the same time coiling it into a
spiral. It is then coated with a pyroinsulator formed of some oxide or other com-
pound or material, such as asbestos, that is fused with difficulty. The oxides are
preferably dissolved in an acid and applied to the helix, and then the salt decom-
posed by heat. The helix is compressed into a compact cylindrical form, and it is
rendered incandescent by the passage of the electric current, and by its expansion
it is made to regulate the electric current and prevent injury to the light giving
body, as in a Provisional Specification heretofore filed by me. A resistance or
rheostat is thrown in or out of circuit, either automatically or in directing the
current through the candle, so as to maintain uniformity of resistance.
The aforesaid helix may be polished on the outer edges of the coil, or a cup be
used around the same. When finely divided iridium or similar metal not easily
fused is mixed with an oxide, such as the oxide of titanium, iron, or other metal
that acts as a conductor when highly heated, the resistance is lessened in proportion
to the heat, and by properly proportioning the mixture the bar or candle is self
regulating to prevent the heat becoming too great.
The conductors are largest near the source of electric energy, and decrease in
size in proportion to the number of lights that have been and are to be supplied.
I provide a magnetic safety switch actuated by an electro magnet, so as to supply
to each building only the current required, and to disconnect the circuit if the
current is too powerful or the wires in the building come into contact. I also
provide for storing the electric current or energy, so that the same may be used as
required. This is done by the use of secondary batteries, and there are devices for
shifting the current from one secondary battery to another periodically, so that one
may be in use while the other is being charged from the main circuit. Induction
coils when used should be placed with their primary coils in a shunt from the main
conductors with current shifting devices, and the secondary currents developed by
induction are used in the electric candles.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Alva Edison in the Great Seal Patent Office on the 28th June
1879.
THOMAS ALVA EDISON, of Menlo Park, in the State of New Jersey, United States
of America. "IMPROVEMENT IN MEANS FOR DEVELOPING MAGNETISM AND
ELECTRIC CURRENTS, AND IN APPARATUS FOR ILLUMINATING BY ELECTRICITY."
One part of this Invention relates to an electric lamp or burner made from a wire
or strip of platina, platina-iridium alloy, or other metal which fuses at a high
temperature. This wire or strip I coat with an oxide of metal, such as cerium,
lime, magnesia, or other metal or material which will not be injured by a high
degree of heat; this coating I term "pyroinsulation."
The wire or strip may be pyroinsulated by dissolving the oxide in an acid, coating
the wire or strip with the solution, and then passing the wire or strip through heat
from a flame or otherwise, to decompose the solution and cause the deposit of the
oxide upon the wire or strip.
If the burner is made of wire, the wire after being pyroinsulated is wound upon
a spool or cylinder of lime or other infusible material, and when the burner is
placed in an electric circuit and the circuit closed, the electricity passes through the
entire length of the wire of the burner and brings it to incandescence. The metallic
oxide forms a pyroinsulating coating that protects the metal of the wire, and
renders it more difficult to fuse, and prevents the electric current passing from one
coil to the next, thereby compelling the current to travel the entire length of the
wire.
If the burner is made from a strip of metal, the same should be thicker at one
edge than the other, so that it may be rolled to an uniform thickness, at the same
time that it is coiled into a spiral. The strip of metal should be thin, so as to
obtain considerable length in a short spiral. The spiral or helix thus made is pyro-
insulated, as aforesaid, and then compressed into a compact cylindrical form.
Sometimes the pyroinsulating material is placed as a layer between the coils of
the spiral or helix.
When the expansion and contraction of the burner a is made to regulate the
amount of current to the burner, the helix or spiral is placed between heads 2, 3,
as shown in Fig. 1, and the rod b is connected to the upper head 3 and also to the
lever c. The lower head 2 is supported by the legs 4, 4.
The spiral expands or
contracts as a whole, and gives motion by the rod b to the bent lever c, which latter
opens and closes the circuit at 5. When c is away from 5 the current enters by
wire 7 and passes to the burner, thence by rod b, lever c, and wire to the line. If
the current becomes excessive the heat expands the spiral, raises the rod b, and
moves the lever c into contact with 5, short circuiting or shunting the current, so
that it passes by the route having the least resistance, going by 7, 9, 5, c, and 8 to
A resistance coil equal to the resistance of the burner may be placed in this
Jine.
short circuit.
The lever e is a safety device which closes the short circuit through the screw 10,
in case c and 5 should fail to make electrical contact.
Fig. 2 shows in enlarged size a burner made of the flattened pyroinsulated wire,
the exterior of the burner may be polished, or the pyroinsulating material may be
wholly removed from said exterior surface.
Fig. 3 shows a perspective view of a burner composed of six helices of pyroinsu-
lated wire, each helix being wound upon a spool of infusible material, such as lime,
and the spools secured to a divided disk of the same material supported upon
metallic rods or half cylinders. The wires 7 and 8 of the line connect to opposite
helices as shown, and the helices are connected to each other, hence the current is
obliged to pass through all the helices, and brings each helix to the same degree of
incandescence.

page_text: The thermal regulators set forth in my British Patent of Oct. 23, 1878, may
be used for regulating the current to burners made like those in Figs. 1, 2, 3,
the special feature of this part of my present Invention relating to the burner made
of a wire or strip of metal coated with a pyroinsulating material for the purposes
aforesaid.
This pyro-insulating coating allows of very fine wire being used for the burner,
hence several layers of the wire may be wound upon the spool of infusible material,
and the burner will have a resistance of several hundred ohms which permits of
several hundred burners or lamps being connected quantitively in multiple arc,
without requiring large main conductors.
In Fig. 4 the burner a is made of pyroinsulated wire, and said burner is sur-
rounded by a metal cylinder a' which becomes incandescent from the heat of the
burner, and radiates the light. The expansion bar b', when the beat of the burner
exceeds a pre-determined point, moves the lever c, and opens the circuit between c
and 5, and closes the short circuit 9 through 5 and 6, in which short circuit there is
a resistance R equal to that of the burner; this arrangement of thermal regulator
and circuits is similar to that shown in my aforesaid Letters Patent.
All the burners of wire or metallic strips shown in my aforesaid Letters Patent
may be coated with the pyroinsulating material.
In Fig. 5, I have represented a means for pyro-insulating the wire, consisting of a
carriage fitted to move back and forth under the stretched wire, and carrying a
sponge e moistened with the pyro-insulating solution, and a lamp for drying the
coating applied to the wire. The sponge is moistened with a soluble salt of the
pyroinsulation, such as the nitrate, oxalate, or acetate of lime, zirconium, magnesium,
or cerium, and its group of metals, whose oxides are infusible after being heated.
The first passage of the wire in contact with the moistened sponge lays a very thin
layer of the solution on the wire, and the heat from the flame which is behind the
sponge serves to decompose the salt, driving off the acid and leaving an adherent
oxide upon the wire. This operation may be repeated many times, each time the
deposit becomes thicker, until the oxide has reached a thickness of about one third
that of the wire itself. The wire should be wound upon a spool having a large
circumference before being wound upon the spool of the burner to prevent the
cracking of the oxide.
In some instances I make a burner or candle of finely divided iridium or other
metal that is not easily fused, mixed with an oxide of titanium, iron, or other metal
which acts as a conductor when highly heated; this is to be moulded into the
desired form, and by properly proportioning the mixture, the current to the burner
is regulated by the heat of said burner, the resistance being lessened in proportion
to the heat.
Another feature of this Invention relates to the arrangement of the main con-
ducting wires so as to obtain a complete metallic circuit, and at the same time take
advantage of the conductivity of the earth, so that the mass of metal in one of the
conductors may be reduced; the earth and metallic conductor serve at the same
time as a protection for the insulated conductors. Fig. 6 is a diagram illustrating
the connections.
The magneto electric machines may be of any suitable character and driven by
power. They may be arranged between the two main conductors A, B, in ranges
or multiple area of three, four, or more in each, and the connections should be for
intensity. I have represented four such magneto electric machines M. in each range.
A is a tube laid in the earth and preferably of iron, and it forms together with the
earth one half of the circuit; within this tube is an insulated conductor B, pre-
ferably of a number of strands of copper twisted together in the form of a cable, one
strand of the cable being dropped, say, every 100 feet, so that at the extreme end of
the circuit there shall be but a single strand. This cable is insulated from the tube
by any cheap or economical insulation, such as tar or asphaltum. A branch tube
containing a single strand from the cable is to enter each house or building, and

page_text: from the basement smaller wires are run to the various parts of the house where
the lights are required.
Each lamp is to be provided with a switch 22 so that it may be disconnected
from the conducting wires.
The electric generators at the central station are provided with constant field of
force magnets, the helices of which are in the electric circuit, hence if all the lamps
feeding from the main conductors are disconnected by their switches the circuit will
be broken and no current passes through the conductors leading from the station to
the lights, hence the steam engine driving the magneto machines runs lightly and
with the expenditure of a very small amount of force. If now the switch of a
single lamp is turned the lamp is connected to the branch wires from the main
conductors, the circuit is closed, and only sufficient current passes from the central
station to supply that lamp because the external resistance determines the amount
of current. In this way the current will be proportioned to the number of lamps
in the circuit. Each lamp I prefer to contain a resistance, when incandescent, of
1000 ohms. As before described, the connecting of one or more lamps causes a
sufficient amount of current to be developed at the central station to keep the same
incandescent, it follows that if the machines at the station are arranged expressly.
for tension and quantity many hundreds of lamps may be placed in circuit between
the main conductors, the reduction of resistance upon placing cach lamp in circuit
drawing the proper quantity of current from the station, hence the greatest economy
possible is obtained by causing all the resistance outside of the main conductors to
be light giving resistances.
In Fig. 7 I have shown a safety device for shutting off the current from the main
wire to the house in case the wires should get "crossed," or from any other cause
the current passing to the house should become in excess of that required for the
burners. m is an electro-magnet in the same circuit as the burners. The armature
lever of this magnet is kept upward by means of a spring resting against an adjusting
screw, and the tension of this spring is to be such that the lever will not be attracted
until the current passing through the inagnet reaches a certain intensity. When
so attracted the lever is separated from m³, latched at m³, and the circuit broken to
the house, hence no injury results to the burners from the excess of current on the
line. Word must now be sent to the central station, and when the fault is remedied
the lever m³ is unlatched by hand and the circuit again closed to the house by the
lever m³ coming in contact with m².
Another part of this Invention relates to means for storing the electric current
or energy so that the same may be used as required. This is done by the use of
secondary batteries, and there are devices for shifting the current from one secondary
battery to another periodically so that one may be in use while the other is being
charged from the main circuit.
In the diagram Fig. 8 the circuit connections are illustrated. Fig. 9 is a
perspective view of the switch; and Fig. 10 is a side view of the secondary
batteries.
The secondary batteries A³, B³, are of any desired construction. I prefer and use
two sheets of lead wound together into a square or cylindrical form and immersed
in acidulated water in a closed case. The main line a³ is connected with any
magneto-electric machine or other source of electric energy, and 63 is the return line
or earth connection. The main line a* is connected by the wires c³ to the secondary
batteries A³, B³, and the return wires d³, e², pass through the switch fand wire i
to 6%
The electric lamps are represented in branch circuits between the wires h and k.
The wire h connects to one end of the secondary batteries A³, B³, and the wire k
connects to the switch f.
The switch fis preferably cylindrical with two insulated half cylinders 14 and 15
against which the springs of c², d², rest, and from these half cylinders are metallic
connections to the insulated disks 16 and 17 respectively, against the peripheries of

page_text: which the springs of i, k, rest, and this switch can be rotated periodically by a
handle, or by clock-work, or other suitable means.
When the switch fis in one position the main circuit is closed through a², c², As, d³,
14, 16, and i to 62, and the secondary circuit is closed from B³ through h, lamps a,
wire, switch 17, 15, and wire e to B³. When the switch f is in the other position
the main circuit from a² passes by c² to B³, and by e³, 14, 16, and i to 62, while the
secondary circuit from A³ is by h through lamps a, wire k, 17, 15, and wire d² to A³,
so that when the secondary battery B is furnishing the accumulated electricity to
the lamps a the main current is charging the secondary battery A³, and vice versa.
When a secondary battery is fully charged the decomposition of the liquid
commences and gases are developed. I avail of this to actuate a circuit regulator
and disconnect the main current.
The two closed cases in which the secondary batteries are placed are provided with
tubes 8 passing to a chamber beneath a flexible diaphragm t, and in the metallic
circuit there is a switch or lever u that is acted upon to break the electric circuit
to the secondary batteries when the gases have accumulated sufficient to move said
diaphragm. The accumulated gases combine, and in so doing maintain the electric
action of the secondary batteries, and the pressure decreases and the circuit is again
closed by the lever u.
Having now described the nature of the said Invention, and in what manner
the same is to be performed, I declare that
I claim as my Invention,-
First. An electric lamp or burner made of a wire or strip of metal coated with
pyroinsulating material, substantially as and for the purposes specified. Second.
The electric lamp or burner made of layers of metal with intervening pyro-insula-
tion, substantially as specified.
Third. The combination with a burner formed of pyroinsulated metal the metal
case a surrounding the burner and made incandescent by the heat thereof, sub-
stantially as specified.
Fourth. The method of pyroinsulating the wire or strip of metal for the conductor,
consisting in passing the wire or strip through a solution of lime, magnesia, or
similar material, and then through heat from a flame to effect decomposition of the
solution, as specified.
Fifth. The insulated metallic conductors within a metallic case which forms with
the earth the return circuit, substantially as specified. Sixth. The combination
with electric lamps and a main circuit of two secondary batteries and circuit con-
nections and switch, substantially as set forth, to alternately change the main und
secondary circuits, substantially as specified.
Seventh. The combination with a secondary battery and its enclosing case of a
diaphragm or similar device acted upon by the accumulation of gas pressure, and a
switch or lever moved by such diaphragm to disconnect the main circuit from the
secondary battery, substantially as set forth. Eighth. An electro-magnet m in the
same circuit as the lamp or burners in combination with the armature lever m³,
latch m³, and contact m¹, substantially as and for the purposes set forth.
In witness whereof, I, the said Thomas Alva Edison, have hereunto set my
hand and seal, this Fourth day of June, A.D. 1879.
Witnesses,
THOMAS ALVA EDISON. (LS.)
CHA³. H. SMITH, 140, Nassau St., N.Y.,
WILLIAM G. MOTT, 140, Nassau Str., N.Y.