IMPROVEMENTS IN THE MODE AND APPARATUS FOR WORKING RAILWAY SIGNALS
Year: 1870

page_text: LETTERS PATENT to William Henry Precce and William Edward
Langdon, both of the Town and County of Southampton, Electrical
Engineers, for the Invention of "IMPROVEMENTS IN THE MODE
AND APPARATUS FOR WORKING RAILWAY SIGNALS."
OF
Scaled the 25th October 1870, and dated the 3rd May 1870.
PROVISIONAL SPECIFICATION left by the said William Henry Precce
and William Edward Langdon at the Office of the Commissioners
of Patents, with their Petition, on the 3rd May 1870.
We, WILLIAM HENRY PREECE and WILLIAM EDWARD LANGDON,
both of the Town and County of Southampton, Electrical Engineers,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE MODE OF AND APPARATUS FOR WORKING RAILWAY SIGNALS," to be as
follows:-
The object of this Invention is so to work railways as to diminish the
risk of danger to passing trains. To this end we propose to lock the

page_text: lever used for working the semaphore or other signal at one station, and
thus prevent its being put in action until released by the signalman at a
distant station. This we effect by the aid of an arrangement of apparatus
to be presently described, which is actuated by electro-magnetism. We
also propose to prevent a change of signal being effected from "blocked"
to "clear" before the pointsman has first adjusted the points and given a
clear road for the advancing train, and we further propose to prevent the
alteration of the signal until the train has passed the distant signal
station.
The hand lever used for working the signal for the engine driver is
fitted with a steel catch piece which when the lever reaches the end of
its throw catches on to a stop suspended from a rock lever provided with
a counterweight. Keyed to the fulcrum of this rock lever is the
armature of a pair of electro-magnets connected by the line wire with
the distant signal station. When a current of electricity is admitted to
the electro-magnets by the instrument at the distant station the armature
will be attracted by the electro-magnet, and the rock lever being con-
sequently raised the stop will be drawn out of contact with the catch
piece of the hand lever. The signalman will now be enabled to set his
signal by drawing over his hand lever in the usual way. To prevent the
signal.being altered before the points have been properly set we propose
to connect the points electrically with an instrument similar to that just
described, thus enabling the pointsman instead of the signalman at the
distant station to release the hand lever used for working the signal.
Or the circuit may be completed by the flange of an engine wheel
passing over a commutator, and the electro-magnet being set in action
the stop will be withdrawn from the catch piece of the hand lever,
as before explained, leaving the signalman at liberty to set his signal.
"
A further object of our Invention is to provide a signalman with
evidence that the signal of "clear or "blocked" which he has trans-
mitted to a distant station has been duly received. This end we attain by
causing the man at the distant station who has received the signal to
acknowledge the receipt of the signal by giving the sender of the signal a
visible record of its receipt. For this purpose we provide in each signal
box a recording instrument through which the signal is sent forward, the
current from which instrument will indicate to the receiver what signal
has been sent, that is, whether he has signalled the semaphore "on" or

page_text: 66
off." The duty of the receiver of this will be not only to set his own
signal agreeably to the signal sent, but also by a return current to
set the recording instrument of the sender in conformity with the signal
received.
"
The recording instrument is constructed as follows:-On a back board
is mounted a commutator, the spring tappet lever of which carries two
stop pins which are intended to operate a pair of tumbling levers, each of
which is provided with a catch, these catches take respectively on to the
catch of a spring armature of an electro-magnet, and upon the tumbling
levers is marked respectively "on" and "off," denoting "blocked" and
clear;" these tumbling levers, as the commutator is set, are one or other
of them thrown up into the position where they are held by their
respective armatures. Fitted to the back board is a face plate, in the centre
of which is an opening for exliibiting to the signalman a record of the
signal which he has transmitted. Thus, supposing that he has signalled
that the line is "clear," the man receiving this signal will immediately
acknowledge it and cause the tumbling lever of the receiver's recording
instrument carrying the word "off" to fall back by its own weight and
present the word "off" to the opening in the face plate. On the contrary,
in signalling "blocked" the tumbler carrying the word "off" will be
lifted out of the way by the spring tappet lever, and the other tumbler
will by the return current be released from its armature and falling back
will present the word "
on" before the opening in the face plate. These
results are obtained by passing a current of electricity through one or
other of the electro-magnets and thereby causing that magnet to attract
its armature. The armature being drawn down will release the catch
of the tumbling lever, which by its own weight will fall into the recording
position, as above explained. The current of electricity passing from
the electro-magnet of the recording instrument will enter the line wire,
proceed to the signal indicator at the distant station, will sound the bell
of that indicator to arrest the attention of the signalman, and will set his
Indicator or semaphore arm.
From the above explanation it will be understood that both the
recording and the semaphore instruments are worked through one and the
same wire.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Henry Preece and William Edward
Langdon in the Great Seal Patent Office on the 3rd November
1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, WILLIAM
HENRY PREECE and WILLIAM EDWARD LANGDON, both of the Town
and County of Southampton, Electrical Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Third day of May, in the year of our
Lord One thousand eight hundred and seventy, in the thirty-third year
of Her, reign, did for Herself, Her heirs and successors, give and grant
unto me, the said William Henry Preece and William Edward Langdon,
Her special licence that we, the said William Henry Precce and
William Edward Langdon, our executors, administrators, and assigns,
or such others as we, the said William Henry Preece and William
Edward Langdon, 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 THE MODE OF AND APPARATUS FOR WORKING
RAILWAY SIGNALS," upon the condition (amongst others) that we, the said
Willam Henry Preece and William Edward Langdon, our executors or
administrators, by an instrument in writing under our, or their, or onc
of their hands and scals, should particularly describe and ascertain the
mature 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 immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said William Edward Langdon, on
behalf of myself and of the said William Henry Preece, do hereby
declare the nature of our said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in
and by the following statement, reference being had to the Drawing herc-
unto annexed and to the letters and figures marked thereon (that is to
say):-

page_text: The object of this Invention is so to work railways as to diminish tho
risk of danger to passing trains. To this end we propose to lock the
lever used for working the semaphore or other signal at one station, and
thus prevent its being put in action until released by the signalman
at a distant station. This we effect by the aid of an arrangement.
of apparatus to be presently described which is actuated. by electro-
magnetism.
We also propose to prevent a change of signal being effected from
"blocked" to "clear" before the pointsman has first adjusted the points
and given a clear road for the advancing train and we further propose
to prevent the alteration of the signal until the train has passed the
distant signal station.
་
In the accompanying Drawing Fig. 1 shews in longitudinal section;
and Fig. 2 in transverse section, the instrument which we employ for
locking the hand lever, by which the semaphore is worked. A is the
hand lever used for working the semaphore or other signal by which the
engine driver is instructed as to the condition of the line. This lever is
fitted with a steel catch piece B which plays through a slotted transverse
vertical plate C forming part of the bracket or support carrying an
electro-magnetic instrument D; a is a stop piece pendent from and
actuated by the electro-magnetic apparatus. This stop a hangs across
the slot of the plate C and is suspended from a rock lever b. provided
with a counter-weight. Vertical guides or shoulders are formed at the
back of the plate C' to prevent the stop piece from moving endwise and
thus retain it in such a position that when the lever A reaches the end
of its throw and the catch piece is protruded through the slot of the
plate C the stop piece may be ready to drop into the catch and secure
the lever. A rigid arm projecting from the rock lever is made fast to
an armature c which hangs on pivot screws d carried by the Standards e.
These screws d therefore form the fulcrum for the rock lever b. In
front of the armature c is placed a pair of electro-magnets connected
by the line wire with the distant signal station. When a current of
electricity is admitted to the electro-magnets by the instrument at the
distant station, the armature will be attracted by the electro-magnets
and the rock lever 6 being consequently raised, the stop a will be drawn
up from the catch piece B of the hand lever, and that lever will there-
fore be unlocked. The signalman will now be enabled to lower his
signal by drawing over his hand lever in the usual way.
To prevent

page_text: the signal being altered before the points have been properly set we
propose to connect the points electrically with an instrument similar to
that just described, thus enabling the pointsman instead of the signalman
at the distant station to release the hand lever used for working the
signal. Or the circuit may be completed by the flange of an engine
wheel passing over a commutator, and the electro-magnet being set in
action the stop will be withdrawn from the catch piece of the hand
lever as before explained, leaving the signalman at liberty to set his
signal.
A further object of our Invention is to provide a signalman with
evidence that the signal of "clear" or "blocked" which he has
transmitted to a distant station has been duly received. This end we
propose to attain by causing the man at the distant station who has
received the signal to give the sender of the signal a visible proof or
record of its receipt when acknowledging the receipt of the signal.
For this purpose we provide in each signal box a recording instrument
through which the signal is sent forward, the current from which instru-
ment will indicate to the receiver what signal has been sent, that is,
whether he has signalled the semaphore "on" or "off." The duty of the
receiver of this will be not only to set his own signal agreeably to the 2
signal sent but also by a return current to set the recording instrument
of the sender in conformity with the signal received.
Fig. 3 shews our improved recording instrument in front view; Fig. 4
represents the instrument with the face removed, the better to show its
internal construction, and Fig. 5 is a vertical section of the sanie.
Appended to Fig. 4 are diagrams shewing the electrical connection of
the recording instrument at one station with a similar recording instru
ment situate at a distant station, and also the connection of these two
recording instruments with their respective semaphore instruments and
with their batteries.
2
3
The recording instrument it will be seen consists of a commutator
fixed on a back board A and connected by a single line wire B to the
distant recording instrument A* and to its semaphore instrument C by
a wire C*, and to its batteries D and E by wires D* and E*, which
batteries are connected to earth as usual. F is a spring tappet lever 3
mounted on a swivel joint midway between two clectro-magnets and
carrying two stop pins f. These stop pins are intended to operate a
pair of tumbling levers G, G*, mounted on centres carried by the back
:

page_text: 66
board and set at opposite sides of the tappet lever. Each of these
tumbling levers is provided with a catch near its fulcrum end which
catches take respectively on to the catch of a spring armaturc h of an
electro-magnet H. The free ends of these tumbling levers G, G*, carry
dises marked respectively on" and "off" denoting "blocked" and
"clear". These tumbling levers as the commutator is set by the move-
ment of the lever F to the right or to the left are one or other of them
thrown up by their respective stop pins into an elevated position where
they are held by their respective armatures / until released, as will be
presently explained. Fitted to the back board and covering the mecha-
nism just described is a face plate I, in the centre of which is an opening
for exhibiting to the signalman a record of the signal which he has
transmitted. The normal position of the spring tappet lever F is in
contact with one or other of two metallic conductors K, K*, which are
connected respectively to the wire coils around their adjacent electro-
magnets. These coils are also connected by conducting wires with a
semaphore instrument C, and the spring tappet lever F is in permanent
connection with the line wire B. Within range of the spring lever F
are also two other metallic conductors L, L*, which are severally
connected with their respective batteries D and E. Projecting from
the inner face of the spring lever Fis a metallic pin f*, and by pressing
on a knob which the spring lever carries this pin may be brought into
contact with one or other of the metal conductors L, L*. Supposing
now that the attendant at the near station desires to signal by means
of the commutator to the distant station that the line is clear he will
throw the spring lever F into the dotted position of Fig. 4, and pressing
on the knob of that lever will cause the pin f* to come into contact
with the metallic conductor L*, and by the same motion the lever will
be lifted off from connection with the metallic conductor K* and bring
the battery E into circuit with the distant signal apparatus. The current
flowing from the battery E will now pass along the lever F and by
the line wire, B to the recording instrument A* and thence to the
semaphore and will set that signal at " 'clear". The duty of the man
receiving this signal will be immediately to acknowledge it and cause
the tumbling lever of the transmitter's recording instrument carrying
the word " off" to fall back by its own weight and present the word
"off" to the opening in the face plate. This will be effected by the
man at the distant station simply pressing the lever F, and on depressing
the pin f* as before described the current will be caused to flow through

page_text: the coils of the magnet H* and attract the armature *, thereby dis-
engaging the lever G* and allowing it to fall by its own weight towards
the centre of the commutator. If on the contrary "blocked" is
required to be signalled the tumbler carrying the word "off" will be
lifted out of the way by the act of bringing the spring tappet lever
into the drawn position of Fig. 4. The attendant now on pressing the
pin finto contact with the metallic conductor L will cause a current
to flow from the battery D through the commutator and along the line
wire B to the commutator at the distant station, whence it will pass to
the semaphore apparatus at that station and so to earth. The attendant
at the distant station will now by depressing the lever of his instrument
send a return current by the line wire B to the commutator A which
current will pass to the spring lever F of that instrument and through
it to the metallic conductor K whence the current will pass through
thic coils of the electro-magnet H and cause that magnet to attract the
armature and thereby release the tumbler G, allowing it to fall forward
and bring the word "on" to the centre opening of the plate I, the
current passing meanwhile by the wire C* to the semaphore apparatus C
and striking the bell of that instrument to give the attendant an audible
signal and flowing thence to earth. Thus it will be understood that by
our improved system the sender of a signal will require to have, and
will receive, a visible and a permanent answer to that signal, which
signal will remain in sight until it is displaced by the attendant in the
act of sending a contrary signal. From the above explanation it will
be understood that both the recording and the semaphore instruments are
worked through one and the same wire.
Having now set forth the nature of our Invention of "Improvements
in the Mode of and Apparatus for Working Railway Signals," and
explained the manner of carrying the same into effect, we wish it to
be understood that under the above in part recited Letters Patent we
claim,―
Firstly. Locking the levers used for working semaphore and other
signals by the aid of electric currents in the manner and for the purpose
above described.
Secondly. Setting the semaphore signal apparatus at a distant station
and receiving therefrom evidence of such setting by means of com-
mutators communicating through one and the same line wire as
described.

page_text: Thirdly. The construction of instruments as above described for
ecording while acknowledging the signals transmitted.
In witness whereof, I, the said William Edward Langdon, have
hereunto set my hand and seal, the Second day of November,
in the year of our Lord One thousand eight hundred and seventy.
WILLIAM EDWARD LANGDON. (L.S.)