IMPROVEMENTS IN ELECTRO-MAGNETIC INDUCTION MACHINES
Year: 1864

page_text: LETTERS PATENT to Jacob Baynes Thompson, of No. 8, Rothwell Street,
Regent's Park Road, in the County of Middlesex, for the Invention of
"IMPROVEMENTS IN ELECTRO-MAGNETIC INDUCTION MACHINES."
Sealed the 30th September 1864, and dated the 9th April 1864.
PROVISIONAL SPECIFICATION left by the said Jacob Baynes Thompson
at the Office of the Commissioners of Patents, with his Petition, on the
9th April 1864.
I, JACOB BAYNES THOMPSON, of No. 3, Rothwell Street, Regent Park
Road, in the County of Middlesex, do hereby declare the nature of the
Invention for "IMPROVEMENTS IN ELECTRO-MAGNETIC INDUCTION MACHINES," to be
as follows:-
This Invention has for its object the so arranging electro-magnetic induction
machines as to make them suitable for use for ordinary telegraphic purposes,
the machine itself making and breaking the primary battery circuit, and also
working a commutator so as to lead all the positive induced currents to one
conducting wire or channel, and all the negative induced currents to another
conducting wire or channel; hence when these wires or channels are con-
nected at a distance, a current which is practically continuous flows through
them, and this current may be used for telegraphic purposes just as a direct
battery current is now commonly used.
I employ two sets of induction coils arranged end to end and at a short
distance apart; by preference I employ two or an even number of coils in
each set, but this is not essential, as a single coil may be used in place of a
set. If two coils be used in each set, I connect their soft iron cores together

page_text: at their outer ends by a permanent armature, and if several coils be used in
each set I couple their cores together in pairs by permanent armatures.
Between the two sets of coils I arrange an oscillating armature, which, by a
rod connected with it, or otherwise, is made as it moves to and fro to send the
primary current first into the primary wires of one set of induction coils and
then into the primary wires of the other set of coils. The oscillating armature
also moves the commutator; by which the currents induced- in the secondary
wire of the induction coils which are reversed by the changing-the primary
current from one set of coils to the other are nevertheless caused to pass from
the machine always in the same direction, the contacts being changed by the
commutator to compensate for the changes in the direction of the induced
currents. Thus it will be seen that both the primary and secondary currents
are directed by the machine itself, so that the machine is self-acting; for as
soon, as the primary current is allowed to flow, one set of induction coils is
thereby magnetized, and the oscillating armature is drawn towards this set;
then as this motion cuts off the primary current from the first set of coils, and
turns it over to the other set, these in turn draw back the oscillating armature,
which is thus kept in constant motion so long as the primary current is on.
Similarly the proper directing of the induced current is effected by the machine
itself, the commutator being moved by the oscillating armature every time the
primary current is directed from one set of coils to the other. This-self-action
of the machine is an important feature of my Invention. .
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Jacob Baynes Thompson in the Great Seal Patent Office
on the 8th October 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JACOB
BAYNES THOMPSON, of No. 3, Rothwell Street, Regent's Park Road, in the
County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Ninth day of April, in the year of our Lord One
thousand eight hundred and sixty-four, in the twenty-seventh year of Her-reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Jacob Baynes Thompson, Her special licence that I, the said Jacob, Baynes
Thompson, my executors, administrators, and assigns, or such others as I, the said
Jacob Baynes Thompson, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,

page_text: exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
ELECTRO-MAGNETIC INDUCTION MACHINES," upon the condition (amongst others)
that I, the said Jacob Baynes Thompson, my executors or administrators, by
an instrument in writing under my, or their, or one of their hands and seals,
should particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Jacob Baynes Thompson, do hereby
declare the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement thereof, that is to say :-
This Invention has for its object the so arranging electro-magnetic induction
machines as to make them suitable for use for ordinary telegraphic purposes,
the machine itself making and breaking the primary battery circuit, and also
working a commutator so as to lead all the positive induced currents to one
conducting wire or channel, and all the negative induced currents to another
conducting wire or channel; hence when these wires or channels are connected
at a distance a current which is practically continuous flows through them,"
and this current may be used for telegraphic purposes just as a direct battery
current is now commonly used.
I employ two sets of induction coils arranged end to end and at a short
distance apart; by preference I employ two or an even number of coils in
each set, but this is not essential, as a single coil may be used in place of a
set. If two coils be used in each set I connect their soft iron cores together
at their outer ends by a permanent armature, and if several coils be used'in
each set I couple their cores together in pairs by permanent armatures.
Between the two sets of coils I arrange an oscillating armature, which by a
rod connected with it, or otherwise, is made as it moves to and fro to send the
primary current first into the primary wires of one set of induction coils and
then into the primary wires of the other set of coils. The oscillating armature
also moves the commutator by which the currents induced in the secondary
wire of the induction coils which are reversed by the changing the primary
current from one set of coils to the other are nevertheless caused to pass
from the machine always in the same direction, the contacts being changed
by the commutator to compensate for the changes in the direction of the
induced currents. Thus it will be seen that both the primary and secondary
currents are directed by the machine itself, so that the machine is self-acting,

page_text: which carries it sideways, thus forcing one of the contact pieces h³ down into
contact with the spring anvil 7 beneath it. The tooth e¹ in sliding past the
tooth comes against one of the springs h³, which yields to let it pass, and
immediately it has passed the tooth h³ the spring throws the quadrant hover.
The contact piece h¹, which has just been pressed down on to its anvil 7, is
thrown off it whilst contact is being made on the other side. As the rod e and
tooth e return the tooth acts on the other side of the tooth h³, and moves the
quadrant h further over, maintaining the contact between the other contact
piece and anvil 7 until the teeth have again passed each other, thus the two
teeth revolve round each other. It will be seen that the spring anvils are
arranged to yield to the pressure of the contact pieces, and then as the contact
pieces recede to follow until they are stopped by the adjustable buttons m, m..
Short pieces m³, m³, of india-rubber tube are introduced between the anvil.
spring and the button, to prevent noise. At the other extremity of the rod e
is a cross head n, at each end of which a cylindrical hole is bored, and this is
lined with a tube of glass or other insulating material cemented into it, as is
shown at Figure 8, which is a section of one of the ends, full size. o, o, are
metal stems or contact cores, fitted into the cross head; these are passed
through the glass-lined holes, and are fixed, by means of a head or flange on.
the stem coming on one side of the cross head, and a nut screwed on to the.
stem on the other side. Washers of gutta percha prevent metallic contact
between the stems o, o, and the cross head. The stems o, o, are furnished
with glass tips o³, o³, and are passed through holes bored to fit them in the
brass or gun-metal induction ports p¹, p², p³, and p'. Thus it will be seen that
when the rod e is at either extremity of its course the contact cores o will at
that end lie in metallic contact with the ports p, having entered into the holes
in them, whilst at the other end there will be no metallic contact between the
contact cores o and the ports, as the glass tips o' only will enter the holes in
the ports. When the rod e' is moved from end to end of its course the metallic
0. contacts are broken at one end of the contact cores o, and then made at the
other end. Each of the ports is bored with a small hole p* into which
a drop of mercury is placed, to ensure a perfect contact, and the parts
which come together are amalgamated. q, q, are wires, connected with
the contact cores o, and coupling them with the binding screws r, r..
5:8, s, are other binding screws in connection with the secondary wires.
of the induction coils. t, t, are condensers, each consisting of two sheets
of tin foil, sixteen feet long, the surfaces of which are throughout their
whole length placed as close together as is consistent with their perfect
insulation from each other by means of sheet gutta percha or otherwise..

page_text: This being the general construction of the instrument, one of the poles of
the galvanic battery is, as is shown by the diagram, Figure 9, connected
directly to one end of the primary wire of each set of induction coils,
and the other ends of the primary wires are connected respectively to the
spring anvils 1,1; the other pole of the battery is connected with the quadrant
h and its contact pieces h¹, so that as the quadrant rocks, as already described,
the primary current is directed alternately to one and the other of the two sets
of induction coils; one of the strips of foil also in each of the condensers t, t,
is connected directly to one pole of the battery, whilst the other strips are
connected respectively with the spring anvils . The condensers serve to lessen
the spark which passes each time the contact pieces h¹ come down on to the
anvils . The two sets of induction coils are arranged in such manner that
the similar poles come opposite to each other, so that each pair may assist in
demagnetizing the other which the electricity has just left, besides by this
means the making induced current in one pair of coils, and the' breaking
induced current in the other, are caused to flow in one and the same direc-
tion, consequently the secondary wires are enabled to pass continuously
around all the coils. These are connected respectively to the two ports p¹, p³,
and these are connected diagonally to the ports p³, p, so that it will be seen
that the motion of the rod e constantly reverses the connections between the
ends of the secondary wires and the binding screws s, s, and it is from these
binding screws that currents for telegraphic or other purposes are taken.
The reversal of the connections of the binding screws 8, 8, with the secondary
wire takes place, as will be observed, when the rod e is at mid-stroke or there-
about, and the reversal of the battery connections with the primary wires:
takes place near the end of the stroke of the rod e, so that when the latter
reversal takes place there is always metallic connections for the free flow of
the induced currents produced at the commutator to the binding screws 8, 8,
and so to the telegraphic wires or other conductors. In order to prevent the
oscillating armature d actually striking the poles of the coils, vulcanized india-
rubber buffers T, T, are employed: These are pieces of vulcanized india-rubber,
having inclined slits in them, the sides of which are bevelled, and between the
two sides the rod e passes. The india-rubber can be raised and lowered by
adjusting screws T, T¹, and in this way the stroke of the armature may be
regulated so that it may come close up to the poles without actually striking
them. By raising the india-rubber buffers the wider parts of the slits are brought
opposite the poles, and then the armature can approach closer than when by
lowering the buffer pieces the narrower parts of the slits are brought opposite
to the poles. The instrument shown in the Drawing is adapted to work

page_text: through two hundred miles of an ordinary telegraphic line, or to do about the
same work as 50 new cells of Daniells' battery, such as are commonly
employed in working telegraphs. The cores of the coils are in this case
formed of bundles of soft iron rods three-sixteenths of an inch in diameter,
and the bundles are one inch and a quarter in diameter. They are each made
in two parts, being divided in the centre of their length, and a disc of card-
board is introduced between the two parts. In a machine designed to supply
electricity of high tension I should not, however, divide the cores, but make
each in one bundle. Around each of the cores there is a primary or battery
coil consisting of three layers of No. 12 copper wire, covered with silk or
cotton, and over this again is the secondary coil, consisting of 320 yards of
covered copper wire No. 18, and in making up the coils I separate the
layers with a thickness of paper, the layers having been first covered with a
paste made of bees'-wax and turpentine, the paste filling all the interstices in
the layers. The machine can be worked efficiently with three cells of
Daniells' battery, with plates exposing a surface of sixteen square inches. If
it be desired to reduce the intensity and increase the quantity of the induced
current, it may readily be done by coupling the secondary coils each sepa-
rately with the port p³, p³, in place of coupling them in series as is shewn, or,
if desired, they may be coupled to the ports in pairs. In constructing
machines to give greater intensity of current I increase the length of the
secondary coils, and diminish the size of the wire employed. Or, if very great
intensity is required, I make the armature d an electro-magnet, by surrounding
it with battery coils, and in this case, in place of arranging the battery com-
mutator to make and break the battery circuit in the induction coils, I
arrange it simply to reverse the current at each motion, so that each coil may
alternately attract and repel the electro-magnetic armature. I would remark,
that the construction of the self-acting commutators may be much varied, so
long as the changing of the primary and secondary contacts be effected by the
self-action of the machine as described.
In witness whereof, I, the said Jacob Baynes Thompson, have hereunto
set my hand and seal, this Sixth day of October, in the year of our
Lord One thousand eight hundred and sixty-four.
J. B. THOMPSON. (L.S.)