IMPROVEMENTS IN RAILWAY ELECTRICAL SIGNAL APPARATUS
Year: 1873

page_text: LETTERS PATENT to David Alexander Carr and Crawford Peter
Barlow, both of 2, Old Palace Yard, Westminster, for the Invention
of " IMPROVEMENTS IN RAILWAY ELECTRICAL SIGNAL APPARATUS."
Scaled the 22nd July 1873, and dated the 28th January 1873.

page_text: are places (either stations, junctions, or other places on the line) at
which a signal can be transmitted electrically on to the engine or on
to any carriage of a train, by preference through insulated metal bars
placed along the line in the manner described in the Specification of a
former Patent granted to us on the 18th day of May 1872 (No. 1520).
In between these are other places at which a train passing over a lever
or other mechanical or electrical apparatus causes the insulated bar at
the station the train has just left to be uncoupled from a battery, so that
any following train arriving at such station would receive a signal of line
blocked, and at the same time causes the insulated bar at the preceding
station to be coupled up to its battery, so that when a following train
arrives at that station the line clear signal will be given to it. .Or the
arrangement might be reversed, and the line clear signal be given by
uncoupling the insulated bars from the batteries in connection with
them, whilst the line blocked signal is given by coupling up such bars
with their batteries. We prefer however to arrange the apparatus in
such manner that a train after leaving one of the stations at which an
insulated bar is placed along the line, and on passing over the lever or
other mechanical or electrical apparatus should uncouple the insulated
bar at the station the train has just left from a battery with which it
was previously in connection, and at the same time couple up such
battery with a wire leading back to the preceding station, and, by acting
thercon an electrical contact making apparatus, cause the insulated bar
at such station to be again coupled up with its battery. For example
let A, B, shewn on the diagram annexed be two of the places where
(when the train arrives) the signals are received on the engine, and
lot a, b, be the other places between A, B, and B, C, where the levers
are situated. From a to A and b to B a wire is laid, and each wire is
coupled to a battery at A and B respectively. When the extremities
at a and b aro coupled to earth, the signal "line clear" will be given at :
the points A, B, and will be exhibited on the engine when it arrives
there. When the extremities are not coupled up, the signal "linc
blocked" will be given to the points A, B. The coupling-up is effected
by an electro-magnetic apparatus brought in action by the passage of a
train over the lever at each of the preceding points b, c, a wire for this
purpose being laid between a, b, b, c, and so on, and the uncoupling is
effected by the passage of a train over the lover at the points a, b, onc
lever at each of the points doing the two actions. Thus the lever at b
for instance when a train passes over it uncouples the extremities at b,

page_text: and couples the extremities at a.
on.
Now let us suppose a train to be
starting from A, it arrives at the lever at a, passing over it, breaks the
the train
current a, A, thus leaving the signal "line blocked" at A;
going on will arrive at B, and receiving the signal "linc clear" will
proceed, passing over the lever b. In doing so it breaks the current 6, B,
thus leaving the signal "line blocked" at B, and at the same time by
the wire b, a, brings in action the electro-magnetic apparatus at a which
couples up the circuit a, A, thus leaving signal "line clear" at A, and so
Thus without the aid of signalmen the line in rear of a train is
automatically blocked for any predetermined distance, but as exceptional
circumstances might arise which would make it necessary for a man to
have the control, we have connected to the wires from trigger to trigger
(viz., a, b, b, c, and so on) a control instrument, as shown in the diagram,
which indicates whether the portion of line between a and b, or b and c,
as the case may be, is "blocked" or "clear," and by means of which a
signal can be given to the points A or B if required. In connection
with this instrument is a time register which is arranged so as to register
the time of the passage of each train over the triggers and bars, and the
signals given and received by the control instrument and the signals
received by the engine.
The registering apparatus consists of a sheet of paper wound upon a
cylinder connected with a clock in the signal station, this sheet is divided
into spaces to indicate the hours and minutes. A marker is brought
down on to the paper by means of an electro-magnet cach time that the
various signals are given and received.
The arrangement above described is suitable for lines of railway on
which every train stops at each of the stations, but for lines of railway
where this is not the case we modify the arrangement by employing in
addition to the insulated bar situated at each station itself another
corresponding bar at a distance in rear of the station to act as a distance
signal apparatus, so that a train receiving a signal of "line blocked" at
the distance signal may slacken its speed as it comes up to the station,
when it will receive another signal and either go on or stop, according to
the signal it receives.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David Alexander Carr and Crawford Peter Barlow
in the Great Scal Patent Office on the 28th July 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, DAVID
ALEXANDER CARR, and CRAWFORD PETER BARLOW, both of 2, Old
Palaco Yard, Westminster, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-eighth day of January, in the
year of our Lord One thousand eight hundred and seventy-three, in the
thirty-sixth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto us, the said David Alexander Carr and
Crawford Peter Barlow, Her special license that wc, the said David
Alexander Carr and Crawford Peter Barlow, our exccutors, adminis-
trators, and assigns, or such others as we, the said David Alexander Carr
and Crawford Peter Barlow, our 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, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "IMPROVEMENTS IN RAILWAY ELECTRICAL
SINONAL APPARATUS," upon the condition (amongst others) that wc,
the said David Alexander Carr and Crawford Peter Barlow, our
exccutors or administrators, by an instrument in writing under
our or their hands and scals, or under the hand and scal of one of
us or them, 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 Scal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Crawford Peter Barlow, on behalf of
myself and the said David Alexander Carr, do hereby declare the naturo
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 thercof, that is to say :—
The object effected by our Invention is that no train passing along a
line of railway can approach within a limited distance of the preceeding
train without receiving a warning signal.

page_text: be any
The distance at which trains are to be kept apart may
suitablo
distance, and the apparatus works automatically. To obtain this result
we employ a system of apparatus arranged as follows:-Along the line
are places (cither stations, junctions, or other places on the line) at
which a signal can be transmitted electrically on to the engine or on to
any carriage of a train, as described in the Specification of a former
Patent granted to us on the 18th day of May 1872 (No. 1520). In
between these are other places at which a train passing over a lever or
other mechanical or electrical apparatus causes the insulated bar at the
station the train has just left to be uncoupled from a battery, so that any
following train arriving at such station would receive a signal of "line
blocked," and at the same time causes the insulated bar at the preceding
station to be coupled up to its battery, so that when a following train
arrives at that station the "line clear" signal will be given to it. Or
the arrangement might be reversed, and the "line clear" signal be given
by uncoupling the insulated bars from the batterics in connection with
them, whilst the "line blocked" signal is given by coupling up such
bars with their batterics. We prefer, however, to arrange the apparatus
in such manner that a train after leaving one of the stations at which an
insulated bar is placed along the line, and on passing over the lever or
other mechanical or electrical apparatus should uncouple the insulated
bar at the station the train has just left from a battery with which it
was previously in connection, and at the same time couple up such battery
with a wire leading back to the preceding station; and by acting thercon
an electrical contact-making apparatus cause the insulated bar at such
station to be again coupled up with its battery. For example, let A, B,
shown on the Diagram, Figure 1 of the Drawings hereunto annexed, be
two of the places where (when the train arrives) the signals are received on
the engine, and let a, b, be the other places between A and B, and between
B & C where the lovers are situated. From a to A, and b to B, a wire
is laid, and each wire is coupled to a battery at A and B respectively.
When the extremities at a and b are coupled to carth the signal "line
clear" will be given at the points A, B, and will be exhibited on the
engine when it arrives there. When the extremities are not coupled
up, the signal "line blocked" will be given to the points A, B.
coupling up is effected in an instrument called the transmitter
(described below), by an electro-magnetic apparatus brought in action by
the passage of a train over the lever at cach of the succeeding points b, c,
a wire for this purpose being laid between a, b, b, c, and so on, and the
The

page_text: uncoupling is effected by the passage of a train over the lever at tho
points a, b, one lever at each of the points doing the two actions. Thus,
the lever at b, for instance, when a train passes over it uncouples the
extremities at b, and couples the extremities at a. Now let us supposc
a train to be starting from A, it arrives at the lever at a, passing over it, {
breaks the current a, A, thus leaving the signal "line blocked" at A.
The train going on will arrive at B, and receiving the signal "line clear"
will proceed, passing over the lover b. In doing so it breaks the current
b, B, thus leaving the signal "line blocked" at B, and at the same time
by the wire b, a, brings in action the electro-magnetic apparatus at a 1
which couples up the circuit a, A, thus leaving signal "line clear” at A,
and so on. Thus, without the aid of signalmen, the line in rear of a
train is automatically blocked for any predetermined distance; but as
exceptional circumstances might arise which would make it necessary
for a man to have the control, we have connected to the wires from the 1
transmitter to the bars a control instrument, as shown in the diagram,
by means of which a signal can be given to the bars, and thus on to the
engine, if required.
The control instrument is a commutator of the ordinary description
by which the wires from the transmitter to the electrical bars is con-
nected or broken or by which the battery is coupled to the bars. Thus
a signal can be given to the engine independent of the transmitter.
The transmitter we prefer to employ is shewn at Figures 2 and 3 of the
Drawings annexed, and at Figures 4, 5, and 6 are shewn views of lever
apparatus in connection therewith. Other arrangements of lever
apparatus to act in a similar manner may, however, be employed, as, for
example, a lever might be placed between the rails and above them at
such a height that a wheel or cam placed on the axle of the last pair
of wheels of the last carriage could act on the lever and depress it, and
thus move the transmitter.
The lever apparatus shewn at Figures 4, 5, and 6 is composed of a
bar a supported on short lovers b just insido one of the rails, so that tho
bar may, on the passing of a train, be depressed by the flanges of the
wheels and be again raised by counterbalance weights c after the train
has passed; the axis of one of the lovers is prolonged, and has upon it an ;
arm d, from which a connecting rod e passes up to the transmitter and
is there connected to an arm on an axis. Upon this axis is a metal
tongue g, which, when the axis is turned by the passing of a train

page_text: over the bar a descends between two metal springs h, h, and forms an
electrical connection between them during the time that the train is
passing over the bar, and when the train has passed the bar a again
riscs and the axis f is moved back to its former position, one of the
springs is permanently connected to a battery and the other to an
insulated wire leading back to one end of the coils of the electro-magnet
k of a similar instrument at the preceding station, the other end of the
coils being connected to carth. On the axis ƒ is also an arm 7, which,
when the axis is turned as above described by the passing of a train over
the bar a acts by a pin at its end upon a plato m and raises it until a
lever arm on the armature n of the magnet catches beneath and retains
it; the armature end swings upon pivots n, and is drawn away from the
magnet by a small spring as shown.
When a current is sent back from the next station, as above explained,
to the coils of the electro-magnet, the armaturo is drawn towards the
magnet, and the plate m being thus set free drops, and a metal tongue
m² upon it enters between two springs o and forms a metallic connection
between them; one spring is connected to a battery, and the other to an
insulated wire leading to the insulated bar at the station; this bar is thus.
put in connection with the battery, and transmits an "all right" signal to
any passing train; when the train has thus received an "all right
signal and has passed on and moved beyond the lever apparatus before
explained the connections in the transmitter are reversed so that thic
insulated bar is uncoupled from the battery and at the same timo a
current sent back to the electro-magnet of the transmitter at the
preceding station, thereby causing an "all right" signal to be given at
that station.
"
The arrangement so far as above described is suitable for lines of
railway on which every train stops at each of the stations, but for lines
of railway where this is not the case we modify the arrangement by
employing in addition to the insulated bar situated at each station itself
another corresponding bar at a distance in rear of the station to act as a
distance signal apparatus, as shown by the diagram view Figure 1, so
that.a train receiving a signal of "line blocked" at the distance signal
may slacken its speed as it comes up to the station, when it will receive
another signal and either go on or stop, according to the signal it
Receives

page_text: We also employ a time register to register the time of the passage of
cach train over the distance signal bar and to record the signal that has
been there received on the engine. To allow of a signal being thus
transmitted from a passing train to the registering instrument there is,
as shown at Figure 1, a second insulated bar placed along the line just 5
beyond the distance signal, and by means of this bar the signal which
has been there received upon the train is repeated in the manner
described in the Specification herein-before mentioned to the registering
instrument. This instrument consists of a clockwork arrangement to
give a continuous travelling motion to a strip of paper. On this paper 1
marks are made by a metallic point (the paper being metallic paper) or
pencil or any other convenient instrument, the metallic point being
brought down on to the paper by means of an electro-magnet each time
that the various signals are given and received.
One point makes a mark every five minutes (or any other convenient 1
interval of time) the point is moved by an electro-magnet in connection
with the station clock, thus the time of the various signals can be
found by measuring the distance between the time mark and the sigual
mark.
Having thus described the nature of our said Invention, and the manner
of performing the same, we would have it understood that we claim thic
combined arrangement of railway electrical signal apparatus sub-
stantially as described.
stantially as described.
In witness whereof, I, the said Crawford Peter Barlow have hereunto
set my hand and scal, this Twenty-sixth day of July, in the 2
year of our Lord One thousand cight hundred and seventy-
three.