Improved Methods of and Apparatus for Generating and Utilizing Electric Energy for Lighting Purposes.
Year: 1891

page_text: Improved Methods of and Apparatus for Generating and Utilizing
Electric Energy for Lighting Purposes.
I, NIKOLA TESLA, of the Gerlach, 45 West 27th Street, New York, United
States of America, Electrician, do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement :-
My invention consists in a novel method of, and apparatus for producing light by
electricity, as hereinafter described.
Electric currents of very great frequency or of very short duration and also
electric currents of very great difference of potential have heretofore been produced
for various purposes, but I have discovered that results of the most useful
character may be secured by means of electric currents in which both the above
described conditions of great frequency and great difference of potential are present.
In other words, I have found that an electrical current of an excessively small
period and very high potential may be utilized economically and practically to
great advantage for the production of light, and I would here make it clear that I
refer now to a current or what may be termed an electrical effect, of a rapidity of
oscillation or alternation far in excess of anything that has heretofore been
considered desirable or perhaps possible under practical working conditions, and of
a potential greater, perhaps, than has ever been developed and applied to any
useful purpose, and this will be more fully disclosed by the description of the nature
of the invention which is hereinafter given.
The carrying out of this invention and the full realization of the conditions
necessary to the attainment of the desired results involve, first a novel method of
and apparatus for producing the currents or electrical effects of the character
described, second, a novel method of utilizing and applying the same for the
production of light, and third, a new form of translating device or light giving
appliance.
To produce a current of very high frequency and very high potential, certain
well-known devices may be employed. For instance, as the primary source of
current or electrical energy a continuous current generator may be used, the
circuit of which may be interrupted with extreme rapidity by mechanical devices,
or, a magneto-electric machine specially constructed to yield alternating currents
of very small period may be used, and in either case should the potential be too
low, an induction coil may be employed to raise it. Or, finally in order to over-
come the mechanical difficulties, which in such cases become practically insuperable
before the best results are reached, the principle of the disruptive discharge may be
utilized. By means of this latter plan a much greater rate of change in the current
is produced, and the invention, though not limited to this plan, will be illustrated
by a description of the same.
The current of high frequency, therefore, that is necessary to the successful
working of the invention is produced by the disruptive discharge of the accumulated
energy of a condenser maintained by charging the said condenser from a suitable
source of current and discharging it into or through a circuit under proper relations
of self-induction, capacity resistance and period in the well understood ways. Such
a discharge is known to be, under proper conditions, intermittent or oscillating in
character, and in this way a current varying in strength at an enormously rapid
rate may be produced.
Having produced in the above manner a current of excessive frequency, I obtain
from it, by means of an induction coil, enormously high potentials. That is to say,
in the circuit through which or into which the disruptive discharge of the condenser

page_text: takes place, I include the primary of a suitable induction coil, and by a secondary
coil of much longer and finer wire I convert to currents of extremely high
potentials. The differences in the length of the primary and secondary coils, in
connection with the enormously rapid rate of change in the primary current, yield
a secondary of enormous frequency and excessively high potential.
Such currents are not, so far as I am aware, available for use in the usual ways.
But I have discovered that if I connect to either of the terminals of the secondary
coil or source of current of high potential the leading-in wires of such a device,
for example, as an ordinary incandescent lamp, that the carbon may be brought to
and maintained at incandescence, or, in general, that any body capable of con- 1
ducting the high tension current described and properly enclosed in a rarefied or
exhausted receiver may be rendered luminous or incandescent, either when
connected directly with one terminal of the secondary source of energy or placed in
the vicinity of such terminals so as to be acted upon inductively.
Without attempting a detailed explanation of the causes to which this
phenomenon may be ascribed, it is sufficient to state, that assuming the now
generally accepted theories of scientists to be correct, the effects thus produced
are attributable to molecular bombardment, condenser action and electric or etheric
disturbances.
Whatever part each or any of these causes may play in producing the effects 2
noted, it is, however, a fact that a strip of carbon, or a mass of any other shape
either of carbon or any more or less conducting substance in a rarefied or exhausted
receiver and connected directly or inductively to a source of electrical energy such
as described, may be maintained at incandescence if the frequency and potential of
the current be sufficiently high. It may be here stated that by the terms 2
currents of high frequency and high potential" and similar expressions used in
this description is not meant necessarily, currents in the usual acceptance of the
term, but, generally speaking, electrical disturbances or effects such as would be
produced in the secondary source by the action of the primary disturbance or
electrical effect.
66
It is necessary to observe in carrying out this invention that care must be taken
to reduce to a minimum, the opportunity for the dissipation of the energy from the
conductors, intermediate to the source of current and the light-giving body. For
this purpose the conductors should be free from projections and points and well
covered or coated with a good insulator.
The body to be rendered incandescent should be selected with a view to its
capability of withstanding the action to which it is exposed without being rapidly
destroyed, for some conductors will be much more speedily consumed than others.
In the accompanying drawing,
Figure 1 is a diagram of one of the special arrangements which I employ for
carrying my invention into practice.
Figures 2, 3 and 4 are vertical sectional views of modified forms of light-giving
devices that I have devised for use with the improved system.
As all of the apparatus herein shown, with the exception of the special forms of
lamp, is or may be of well-known construction and in common use for other f
purposes, it is indicated mainly by conventional representations.
G is the primary source of current of electrical energy. I have explained above
how various forms of generator might be used for this purpose, but in the present
illustration I assume that G is an alternating current generator of comparatively
low electro-motive force. Under such circumstances, I raise the potential of the
current by means of an induction coil having a primary P and secondary S.
Then, by the current developed in this secondary, I charge a condenser C, and
this condenser I discharge through or into a circuit A having an air gap a, or,
in general, means for maintaining a disruptive discharge.
.
By the means above described, a current of enormous frequency is produced.
My object is next to convert this into a working circuit of very high potential,
for which purpose I connect up in the circuit A the primary P of an induction

page_text: coil having a long fine wire secondary S¹. The current in the primary P¹
develops in the secondary S³ a current or electrical effect of corresponding
frequency but of enormous difference of potential, and the secondary S¹ thus
becomes the source of the energy to be applied to the purpose of producing light.
The light-giving devices may be connected to either terminal of the secondary S
If desired, one terminal may be connected to a conducting wall W of a room or
space to be lighted, and the other arranged for connection of the lamps therewith.
In such case the walls should be coated with some metallic or conducting substance
in order that they may have sufficient conductivity. The lamps or light-giving
devices may be an ordinary incandescent lamp, but I prefer to use specially
designed lamps, examples of which I have shown in detail in the drawing. This
lamp consists of a rarefied or exhausted bulb or globe which encloses a refractory
conducting body, as of carbon, of comparatively small bulk and any desired shape.
This body is to be connected to the secondary by one or more conductors sealed in
the glass as in ordinary lamps, or is arranged to be inductively connected thereto.
For this last named purpose the body is in electrical contact with a metallic sheet
in the interior of the neck of the globe and on the outside of said neck is a second
sheet which is to be connected with the source of current. These two sheets form
the armatures of a condenser and by them the currents or potentials are developed
in the light-giving body. As many lamps of this or other kinds may be connected
to the terminal of S₁ as the energy supplied is capable of maintaining at
incandescence.
In Figure 3 is a rarefied or exhausted glass globe or receiver in which is a
body of carbon or other suitable conductor e. To this body is connected a metallic
conductor which passes through and is sealed in the glass wall of the globe
outside of which it is united to a copper or other wire g by means of which it is to
be electrically connected to one pole or terminal of the source of current.
Outside of the globe the conducting wires are protected by a coating of insulation h
of any suitable kind, and inside the globe the supporting wire is enclosed in and
insulated by a tube or coating k of a refractory insulating substance, such as pipe
clay or the like. A reflecting plate is shown applied to the outside of the
globe b.
This form of lamp is a type of those designed for direct electrical connection
with one terminal of the source of current.
But, as above stated, there need not be a direct connection, as
other illuminating body, may be rendered luminous by inductive
current thereon, and this may be brought about in several ways.
form of lamp for this purpose, however, is shown in Figure 2.
the carbon, or
action of the
The preferred
In this figure the globe b is formed with a cylindrical neck within which a tube
or sheet m of conducting material on the side and over the end of a cylinder or
plug n of any suitable insulating material. The lower edges of this tube are in
electrical contact with a metallic plate o secured to the cylinder n, all the exposed
surfaces of such plate and of the other conductors being carefully coated and pro-
tected by insulation. The light-giving body e in this case a straight stem of carbon,
is electrically connected with the said plate by a wire or conductor similar to the
wire Figure 3, which is coated in like manner with a refractory insulating
material k.
The neck of the globe fits into a socket composed of an insulating tube or
cylinder with a more or less complete metallic linings, electrically connected by a
metallic head or plater with a conductor g that is to be attached to one pole of the
source of current. The metallic linings and the sheet m thus compose the plates
or armatures of a condenser.
If a lamp be made with two carbons or refractory conductors insulated from cach
other, they may be connected to opposite terminals or poles of the generator and
both rendered luminous. In Figure 4 such a lamp is shown. There are two strips
or bodies of carbon e and e¹ each connected with a conducting. wire f sealed in the

page_text: glass. Inside the globe which is exhausted to the highest possible degree the
wires are surrounded by short tubes or cups t, the lower parts of which, when
the wires and carbons join, are filled with a carbon paste to maintain a good
electrical connection between the same. Over this is a filling of fire clay or
similar refractory insulating material.
The carbon strips although not in contact will both become luminous when con-
nected respectively to the two terminals of a source of current such as above
described. In this as in the forms of lamp previously described the carbons in lieu
of being directly, may be inductively connected with the source of current.
This invention is not limited to the special means described for producing the
results hereinbefore set forth, for it will be seen that various plans and means of
producing currents of very high frequency are known, and also means for producing
very high potentials, but I have only described herein certain ways in which I have
practically carried out the invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The herein described improvement in electric lighting, which consists in
generating or producing for the operation of the lighting devices currents of
enormous frequency and excessively high potential, substantially as herein
described.
2. The method of producing an electric current for practical application, such as
for electric lighting, which consists in generating or producing a current of enormous
frequency and inducing by such current, in a working circuit or that to which the
lighting devices are connected, a current of corresponding frequency and excessively
high potential as above set forth.
3. The method of producing an electric current for practical application, such as
for electric lighting, which consists in charging a condenser by a given current,
maintaining an intermittent or oscillatory discharge of the said condenser through
or into a primary circuit and producing thereby in a secondary working circuit in
inductive relation to the primary very high potentials as above set forth.
4. The method of producing electric light by incandescence, by electrically or
inductively connecting a conductor enclosed in a rarefied or exhausted receiver to
one of the poles or terminals of a source of electric energy or current of a
frequency and potential sufficiently high to render the said body incandescent, as
above set forth.
5. A system of electric lighting, consisting in the combination with a source of
electric energy or current of enormous frequency and excessively high potential of
an incandescent lamp or lamps consisting of a conducting body enclosed in a rarefied
or exhausted receiver and connected directly or inductively to one pole or terminal
of the source of energy, as above set forth.
6. In a system of electric lighting, the combination with a source of currents of
enormous frequency and excessively high potential of incandescent lighting devices
each consisting of a conducting body enclosed in a rarefied or exhausted receiver,
the said conducting body being connected directly or inductively to one pole or
terminal of the source of current, and a conducting body or bodies in the vicinity
of said lighting devices connected to the other pole or terminal of said source, as
above set forth.
7. In a system of electric lighting, the combination with a source of currents of
enormous frequency and excessively high potential, of lighting devices each con-
sisting of a conducting body enclosed in a rarefied or exhausted receiver and
connected by conductors directly or inductively with one of the terminals of said
source, all parts of the conductors intermediate to the said source and the light-
giving body being insulated and protected to prevent the dissipation of the electric
energy, as herein set forth.

page_text: 8. An electric lamp, consisting of a rarefied or exhausted globe, a refractory con-
ducting body contained therein and a supporting conductor therefor adapted to be
directly or inductively connected with a source of current.
9. An electric lamp, consisting of a rarefied or exhausted globe, two strips or
bodies of refractory conducting material contained therein, and supporting con-
ductors adapted to connect the said strips or bodies respectively to the opposite
poles of a source of current, as above set forth.
Dated this 19th day of May 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.