IMPROVEMENTS IN ELECTRIC TELEGRAPH APPARATUS
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Samuel Manley Martin, Samuel
Alfred Varley, and Frederick Henry Varley at the Office of the
Commissioners of Patents, with their Petition, on the 24th January
1866.
We, SAMUEL MANLEY MARTIN, of Harrow-on-the-Hill, in the County
of Middlesex, SAMUEL ALFRED VARLEY, of 66, Roman Road, Holloway,
and FREDERICK HENRY VARLEY, of 337, Kentish Town Road, both in the
County of Middlesex, Telegraph Engineers, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN ELECTRIC TELEGRAPH APPARATUS,"
to be as follows:-
We construct our instruments as follows:-We make a series of electro-
magnets, and arrange them in a circle on an iron plate; these magnets are
at equal distances from one another and generally arranged in pairs, so that
they may be opposite one another on each side of the circle and each
magnet connected with the one immediately opposite it; the insulated
wire is so wrapped that the poles of each pair of magnets is of the opposite
character, the one being north and the other south, or vice versa.
number of electro-magnets employed depends upon the number of signals
required, each pair of electro-magnets giving two signals. Over the poles
of the electro-magnets a permanent or an induced magnet is mounted on
an axis terminating in pivots; the lower pivot rests on a spring which
can be adjusted to the requisite degree of strength; on the upper pivot a
The

page_text: light indicator, which may either be a disc of mica or a light pointer, is
fixed. When a disc of mica is used the signals are painted on the disc on
lines radiating from the centre to the circumference. An opaque screen
with a slot on one side is placed above the mica disc, and the signals
arrange themselves under this slot in accordance with the electro-magnets
rendered active. When a pointer is used in place of the mica disc it
moves over a dial on which the signals are painted and takes up its posi-
tion in the same way as described with the mica disc. When a current is
sent through one pair of electro-magnets the mounted magnet immediately
flies round and arranges itself over the electro-magnet and is attracted
down and its motion arrested; on the current being removed the spring
on which the pivot of the mounted magnet rests raises it above the poles
of the electro-magnet, leaving it free to move in any direction; to assist the
action of this spring the electric current after passing through. the electro-
magnets, previously to its entering the earth, is made to pass through
another electro-magnet over which, but insulated from it, a series of
convolutions of insulated wire (technically known as a secondary wire)
are wrapped; the ends of the secondary wire are connected to a series of
coils wrapped on the poles of the electro-magnets, but insulated from them;
on removing the current from the electro-magnets a momentary current is
developed in the secondary wire, and this current passes through the coils
of the electro-magnets. The secondary current passes round the electro-
magnets in the opposite direction to the current previously passing through
and momentarily magnetizes the electro-magnets in the opposite direction;
the effect of this is to counteract any residual magnetism in the electro-
magnets and to liberate the mounted magnet carrying the indicator. In
some cases we substitute circular coils for the electro-magnets, or we coll-
struct the electro-magnets with iron cores that do not come up to the
surface of the coils. When we use coils we prefer placing over each coil
or pairs of coils a permanent magnet of a horse-shoe form; each of these
magnets carries a screen covering 2 letters; a positive current deflects
the magnet in one direction revealing one of the letters, and a negative
current deflects it on the opposite side revealing the other. The electric
current is sent by means of a commutator of the following construction:-
A circular piece of metal is first divided into two halves, one of these
halves is further divided into as many segments as there are line wires.
Two levers insulated froni but attached to one another, which we call the
battery arms, are mounted on a vertical axle and work over the divided
circle, one of them being in contact with the entire half circle; the other

page_text: with the segments on the axle carrying the battery arms; there is a pointer
which points to the signals, which are painted outside the commutator in a
circle. The positive pole of a galvanic battery is connected to one of the
battery arms, the negative pole with the other. The entire half circle
forming part of the commutator is connected to the earth, the segments
to the line wires, on moving the pointer round a half circle a series of
positive currents are sent through the line wires in succession, and on
moving it over the other half a series of negative currents àre sent through
the line wires. When circular coils are used in place of electro-magnets
the commutator is constructed somewhat differently; a circle of ebonite
is placed within the divided circular piece of metal, the battery arms rest
upon this ebonite and are prevented from coming in contact with the
metal segments. Opposite to the centre of the segments notches are cut
in the ebonite ring to allow the battery arms to drop in and come into
contact with the metallic segments when desired. The axis carrying the
battery arms has a vertical motion of about of an inch, and there is a
spring attached to its lower part pulling it down. When sending. with
this commutator the axis is pulled up by means of a handle or button
attached to it, and the pointer moved round until it is opposite the signal,
the battery arms are then allowed to drop into the notches, and a current
is sent which reveals the desired signal. This instrument is intended
chiefly for tunnel circuits and train signalling, but it may be used for a
speaking telegraph; when used for the latter purpose twelve wires will be
sufficient, and the commutator may be made with a series of keys working
like pianoforte keys with letters of the alphabet engraved on them..
The way we construct the instruments when we use circular coils is as
follows: We take. pieces of tube of a slightly larger diameter than the
coils
; we cut this tube into rings of the same width as the thickness of
the coils; we call these rings the coil boxes. We also cut rings out of the
same tube of the width of the space desired between the coils for the magnet
to work between, and call them space rings. We now place the coil boxes,
with a space ring between each pair, into other pieces of tube which fit
tightly over them; these outer pieces of tube hold the coil boxes together
and are of such a length that when placed centrally they cover the space
ring and embrace both coil boxes, leaving the coil boxes projecting an eighth
of an inch, more or less, at both ends. The coil boxes are now clamped
into their places between two plates of metal and soldered to the plates;
the plates are then fixed in their position and attached to one another by
pillars and screws or any suitable way; the plates are now seperated and

page_text: the space rings and the outer pieces of tube which hold the boxes together
removed and the coils placed in the coil boxes. The magnets are mounted
on axles terminating in pivots and work between the two coils; one end
of the axle passes through one of the plates which forms the front of the
instrument, and works in a pivot hole in a bridge. The letters or signals
are painted on the front of the instrument and screens depend from the
axles and cover them until the coils are rendered active by an electric
current passing through them. We employ a modification of the con-
struction just described in some cases which is simpler but not so
sensitive. We take a plate, which may be of metal or any suitable sub-
stance, and bore a series of circular holes through it; the circular coils fit
into these holes flush with the surface; only one circular coil is used in
this arrangement for each horse-shoe magnet. The magnets are mounted
on axles and work over the surface of the coils and carry screens which
cover the signals in the manner previously described; the signals are
painted on thin sheets of cardboard which fit closely to the surface of the
coils. We wish it to be understood we do not claim the use of electro-
magnets nor of circular coils, what we claim is,
First, the mode of liberating a permanent or induced magnet which
has been attracted on to the poles of an electro-magnet by means of a
spring in combination with a secondary current generated in the manner
:described.
Secondly, the use of electro-magnets with the iron core not projecting
up to the surface of the coils.
Thirdly, the methods of constructing instruments with circular coils as
described.