IMPROVEMENTS IN ELECTRO-MAGNETIC MACHINES
Year: 1878

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for the Invention of "IMPROVEMENTS IN
ELECTRO-MAGNETIC MACHINES:" A communication from abroad by Zénobe
Théophile Gramme and Eardley Louis Charles d'Ivernois, both of Paris, in the
Republic of France.
Sealed the 29th November 1878, in pursuance of an Order of the Lord Chancellor,
and dated the 29th March 1878.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 9th March 1878.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN ELECTRO-MAGNETIC MACHINES." A communica-
tion from abroad by Zénobe Théophile Gramme and Eardley Louis Charles d'Ivernois,
both of Paris, in the Republic of France.
This Invention relates to an electro-magnetic machine for the production of
alternate currents of electricity.
The improved machine is composed essentially of,-
1st. A series of electro-magnets arranged radially around a common centre, and
formed in one with a central shaft or axis, to which motion is imparted by means
of an external pulley. These electro-magnets are charged by any suitable current.
2nd. A fixed ring of soft iron covered with copper wire, wound round it spirally,
encircling the system of electro-magnets.
A frame formed of two plates, a base, and several cross bars supports the fixed
ring and also the bearings of the driving shaft.
The core of the fixed ring in lieu of being made in one piece is composed of iron
wire covered with insulating material, such, for example, as cotton, silk, and the
like.
The covering of copper wire is divided into any suitable number of sections.

page_text: The alternate currents available for use are taken from the fixed ring without
the aid of a commutator. A series of separate currents, or a single current of great
intensity, may be produced, as desired, according to the manner in which the
sections on the fixed ring are coupled.
These currents being alternate may be employed for the production of electric
light, for tanning, and all electro-chemical operations which do not require a con-
tinuous current.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Henry Johnson in the Great Seal Patent Office on the
2nd December 1878.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN ELECTRO-MAGNETIC MACHINES." A communication
from abroad by Zenobe Theophile Gramine and Eardley Louis Charles d'Ivernois,
both of Paris, in the Republic of France.
The said Invention relates to improvements in electro-magnetic machines for the
production of currents of electricity alternating in direction (positive and negative).
The nature of these improvements, and the mode of carrying the same into effect,
will be understood by the following description, reference being had to the two
Figures on the Sheet of Drawings hereunto annexed, in which,-
Figure 1 represents an end elevation, with a portion of the end plates and framing
removed, of a machine constructed in accordance with the said Invention; and
Figure 2 is a longitudinal section of the same taken along the line 1, 2, in Figure 1.
The machine is composed of the following parts, videlicet:-
First. An annular armature e of iron wire covered with coils of copper wire,
insulated from each other, and forming a series of bobbins a, b, c, d, absolutely
distinct the one from the other, this being the reverse of the arrangement adopted
in the machine producing continuous currents, constructed upon what is known as
Gramme's system, in which the ends of the wires from the different bobbins are
connected together in order to form an endless wire round the core of the ring.
In lieu of making the external annular armature of one piece it may be formed
by employing a series of segments of iron wire, and covering each of these segments
with coils of copper, the bobbins being then isolated as before. It will then only
be necessary to fasten the whole of the bobbins together and connect them to the
frame in order to obtain the fixed part of the machine.
The peculiarity of the construction of the core of the annular armature, or of the
united segments, consists in the preliminary insulation of the iron wire employed
by covering it with silk, cotton, or any other non-conducting substance.
Second. A series of bar electro-magnets B, B, provided with spreading polar
armatures (shewn most clearly in Figure 1), and carried by discs 7 fixed upon a
central shaft O.
The electro-magnets are alternately of different denominations. These parts
rotate within the annular armature.
1

page_text: Third. A frame composed of two cheeks A, a series of metal tie bars C serving
to give a firm and rigid support to the external armature, and a base D.
The Drawing represents a machine with thirty-two bobbins a, b, c, d, on the
annular armature, and eight radial electro-magnets B. This machine is capable
of supplying thirty-two distinct currents, or sixteen, eight, or four currents as
required.
The whole of the exciting electro-magnets magnetised in any suitable manner
being set in motion by a motor their iron armatures pass in close proximity to the
copper bobbins, in which a current of electricity is required to be induced, and
create in them a current of electricity, the intensity of which is in proportion to the
magnetic power of the electro-inagnets and the rapidity of their rotation, and as the
poles of the inductor are alternately of opposite denominations the currents pro-
duced in each bobbin change their direction continually.
It will be readily understood from a consideration of the theory of induction that
the currents produced in the bobbins a, b, c, d, are of an intensity which varies
according to the position of the armatures fin relation to the bobbins, but that this
intensity is constant in all the bobbins for any one position of the armatures f.
Thus all the bobbins a are affected in a similar manner during a complete revolu-
tion of the electro-magnet, and in the other series b, c, and d, each bobbin is always
affected in the same manner whatever may be the position of the armatures in
relation to the whole of the bobbins in which the electric current is induced (the
currents being however alternately in opposite directions); hence it results that in
order to couple the currents so as to form four circuits of great power it will be
sufficient to couple the eight bobbins a together, and proceed in like manner
with the eight bobbins b, the eight bobbins c, and the eight bobbins d.
The currents may be conducted from the apparatus by connections applied direct
to the stationary bobbins, or more simply to the external binding screws H, serving
to unite the various wires of each group of bobbins.
It is obvious that the annular armature may be divided into a greater number of
bobbins, and that a less number of electro-magnets may be employed than are shewn
in the example illustrated.
The said Invention is applicable to the production of electric light, in combina-
tion with any suitable electric lamp, or electric candle, or apparatus for that purpose,
and also to industrial, chemical, and other operations of every description in which
alternate currents are required.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into
effect, I will observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the herein-before in part
recited Letters Patent is,---
First. The combination of an annular armature entirely covered with copper
wire with a series of electro-magnets rotating within the said armature, the several
parts being constructed and arranged substantially in the manner herein-before
described, and illustrated on the accompanying Drawings.
Secondly. The employment in the said combination of iron wire previously
insulated for the construction of the core of the armature.
In witness whereof, I, the said John Henry Johnson, have to this my Speci-
fication set my hand and seal, the Thirtieth day of November, One
thousand eight hundred and seventy-eight.
J. HENRY JOHNSON. (LS)