IMPROVEMENTS IN RAILWAY SIGNALLING APPARATUS
Year: 1873

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
"IMPROVEMENTS IN RAILWAY SIGNALLING APPARATUS."-A communication
from abroad by Paul Tesse, Henry Lartigue, and Pierre Désiré
Prud'homme, all of Paris, France.
Scaled the 29th July 1873, and dated the 10th February 1873.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents, with his Petition, on
the 10th February 1873.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN RAILWAY SIGNALLING APPARATUS,"
to be as follows :-
This Invention relates to improved electric semaphore apparatus for use
on railways worked on the block system and on single lines, possessing
the following advantages, viz., simplicity, absolute reliance on the signals,
and perfect connection between the latter and the clectric apparatus,
A

page_text: the latter being actuated by the working of the former in such manner
that the apparatus will indicate both when a train enters upon and quits
a block or section of the line, in addition in the case of single lines to
showing whether the line is cleared or blocked by a train travelling in the
opposite direction.
In the accompanying Drawings Figures 1 and 2 show a front and
side view of the electric apparatus.
A, cast-iron box in which are mounted all the parts of the apparatus;
✗, spindle, having a winch handle M at onc end, and a crank arm B in
line therewith at the other end. Spindle X also carries a tappet or
finger D placed at an angle to the hand lever M, as shown, a snail-
shaped cam C, the extreme radius of which is in the plane of the handle
M and crank B, and a wood or ebonite commutator O having seven pro-
jecting keys. One of these keys T connects, by means of a ring-shaped
spring, with the spindle the body of the apparatus and an earth wire.
The six remaining keys a, a, b, b, c, c¹, are coupled together in pairs by
metallic connections. Another spindle Facts as a pivot for two arms at
right angles to each other, one of which consists of a lever J weighted
at G, resting on cam C, a spring being interposed as a cushion to prevent
shocks. The other arm R is in the same vertical plane with finger D,
and is provided at its lower end with a soft iron armature p attached by
a spring, as shown. Arm R is also provided with a slot U, in which
works a pin forming part of a link connecting said arm to an oscillating
stop. Opposite pallet p is placed a Hughes' electro-magnet E composed
of a permanent horse-shoe magnet, the links of which are prolonged by
soft iron cores on which are placed bobbins of covered wire. -
There are four spring contacts around commutator O mounted on an
insulating plate N. Contact L' connects with the line wire L through a
paratonnerre or lightning guard Z, and contact with the bobbins of
the electro-magnet E with the positive pole of the battery which is
1
double with negative pole. At the upper part of box A is placed a
smaller Hughes' electro-magnet H connected with magnet E, the bobbin
on the north pole of the larger electro-magnet, and that of the south
pole of the smaller electro-magnet being connected together and with
the contact E', while the bobbin on the south pole of the larger electro-
magnet and that on the north pole of the smaller electro-magnet are
connected together and with the earth wire T. Opposite electro-magnet
H. is pivoted a bent arm of brass carrying, 1st., a soft iron armature

page_text: "
fixed by a spring, and in contact with the holes of the electro-magnet;
2ndly, an arm Y also provided with a soft iron armature which, when
the armature f is removed from the bobbins, comes into contact with
the limbs of the magnet so that the latter may be always armed;
3rdly, a hammer t and bell T; 4thly, a signal arm bearing the words
signal received" or other indication, which is made to appear opposite
an opening in the front side of the box A. A spring Q tends to oscillate
the same and remove armature ƒ from the poles of the electro-magnet,
when the action of the latter ceases by the passage of a negative current.
A rod S provided with a regulating nut is screwed into arm Y, its other
end being slotted to receive a pin fixed on arm J, thus connecting the
latter with the above apparatus.
The apparatus of corresponding signal stations are connected together
two and two by a conducting wire.
The crank arm B before mentioned is connected by a rod with an
arm of the semaphore signal post. When the arm is upright the signal
arm falls by its own weight, but by partly rotating the winch M it is
brought to an angle of 90 degrees to that it previously occupied, in
which position the arm B is secured by tappet D abutting against
stop P, which prevents the further rotation of spindle X. A pawl W
holds the arm B in this position, and prevents its moving in a backward
direction. If by passing a positive current through electro-magnet E,
the magnetism retaining the pallet fand lever arm R be neutralized, the
latter and with it the part J will oscillate on spindle F, stop P will be
detached from tappet D, the latter thus freed cnabling X to completo a
revolution, and arm B to be returned by the weight of the semaphore
arm to a vertical position. During the latter half revolution of the
spindle the cam C raises lever J, pallet fis again attracted by electro-
magnet E, and the stop P returns to position. During the first half
revolution the commutator puts the line in communication with the
+pole of the battery, which disengages the corresponding apparatus,
while during the latter half of the revolution a negative current is trans-
mitted to acknowledge receipt of the signal by striking bell T¹ with
hammer t, and exhibiting signal disc V. The armature is returned to
contact with the electro-magnet at same time that the hammer tis
raised, and signal V moved out of sight by the downward motion of
lever J, carrying with it the rod S which oscillates arm Y and stretches
Enring

page_text: Figures 3, 4, 5, 6, and 7 show the arrangement of the semaphore
signal post, one of which is to be placed at the sending and receiving
signal stations. The semaphore arms at the sending station are in
duplicate, one of small dimensions colored white, and the other which is
larger being colored red, and provided with a red glass. The two arms
are at right angles to each other. At the receiving station the
semaphore is also provided with two arms, the one being colored white
and of small dimensions, while the other has some special form, such as
an arrow for example. The departure signal arm would be placed at
the top of the post, and the arrival signal at about mid height. A lamp
is arranged to illuminate the red glass when the red arm is horizontal,
and the luminous rays may also pass through a small opening in the
arrow arm when horizontal.
The semaphore arms may occupy two positions at 90 degrees; in the
one case they hang down by their weight, and in the other they are held
in position by a rod or wire cord, connected to the arm B of the clectric
apparatus herein-before described.
The departure signal when set has the red arm placed horizontal, and
the white arm in a vertical position, while when unset the red arm
would hang vertically, and the white arm project horizontally.
"
The arrival when set has the white arm horizontal, and the "arrow"
arm vertical, while when unset the white arm would hang vertically,
and the "arrow arm be horizontal. The signal arms of the two posts
are thus symmetrical, and are both operated in the same way, viz., set by
hand and unset by electricity. S, semaphore signal post; F, iron
mountings for top of post; A, B, principal signal arms; a, b, smaller
O, o, breaks and springs; T, pull rods of signal arms A, B;
t, pull rods of smaller signal arms a, b; E, electric apparatus described
with reference to Figures 1 and 2 in position on the signal post;
K, alarum; Q, q, radius links; L, lamp; f, f¹, ƒ¹¹, Figure 4, lenses;
M, vertical reflector of lens f¹; R, r, reflector for illuminating the lower
part of the signal post; S, G, guides of lamp holder P; p, c, pulley and
chain; J, counterweight.
arms.
It will be seen by reference to Figures 3 and 7 that the pivot of each
signal arm is provided with an angular plate or disc O, against the flat
side of which a spring bears when the arm has reached its maximum
degree of elevation corresponding to an angle of 180 degrees with the

page_text: crank arm B by which the signal is operated. Said signal thus falls
slightly when the movement of the lever arm B is arrested at 200 degrees
(by the tappet D, Figures 1 and 2, abutting against stop P) and is
retained in this position. The spring above mentioned acts as a kind of
break in lowering the signal arm.
The illumination of the semaphore arms is effected by the aid of the
lamp L above referred to, having three lenses, the lens f serving to
illuminate the glazed opening in the large arm A disposed on the same
side as the lamp; the lens f¹ illuminates the glazed opening in the other
large signal arm B by means of a reflector suitably disposed. Beneath
this reflector is a second one of truncated conical form, inclined at such
an angle to the horizon as to reflect downwards a portion of the rays
from the lens f¹, while a third lens f" lights the foot of the post by the
aid of a reflector R also of truncated conical form placed at a suitable
angle.
Figure 8 shows in outline a modified arrangement of signal post
adapted for single line of railway, differing from the foregoing only as
regards the form and dimensions of the lower signal arms and the mode
of operating the same. The engine driver whose attention is directed to
the signal arms on the left hand of the post will stop his train either
when the larger signal arm is in a horizontal position to protect a train
only a short distance in front travelling in the same direction, or when
the smaller signal arm is horizontal to block the line when a train is
on the line travelling in the opposite direction. Thus there can be no
liability of confusion in the signals which are operated in an exactly
similar manner to those for a double line railway before described. In
this latter described arrangement a second lamp will be necessary for
lighting the lower signal arms.
From the foregoing it will thus be understood that by the combination
of the electric apparatus with the semaphores as described the signalman
at the departure station will be assured that the current has passed
through the line with the desired effect of unsetting the semaphore at
the arrival station, inasmuch as the return current is absolutely
dependent on the lowering of the signal arm. When the train has
reached the arrival station the signalman at this point turns the
winch handle, and resets the signal arm which returns to white, and at
same time transmits a current which disengages the semaphore. arm at

page_text: the departure station, which in falling sets the white arm at same time
that a return current advises the arrival station that its signal has been
received. Thus all the working required (which is exactly the same for
the two signal posts) simply consists in giving half a turn to the winch
handle for announcing either the departure or the arrival of a train.
The signals are received without requiring any intermediate agency, but
are always accompanied by an audible signal either by sounding
alarum K in the case of a semaphore signal, or by striking the bell T to
acknowledge the receipt of signals at the corresponding station.
It is unnecessary to observe that each terminal station would bepro-
vided with both a departure and arrival signal post one for cach line, or
in the case of single line railways, one for the up and one for the down
trains.
"
وو
Each intermediate signal station would have a double apparatus, viz.,
four electric apparatus and four semaphore arms placed on the same
post, the two upper arms (right and left) being red, and the two lower
arrow arms. In both arrangements one battery or induction apparatus
is sufficient. Each apparatus is morcover entirely distinct from the
others, and in the arrangement which is preferred on account of its
simplicity two wires are necessary, one for the up trains and one for the
down trains.
The apparatus may however be arranged for use with a single wire,
but in this case it would be necessary to use permanent magnets and to
reverse the currents, the greater cost of which would in some cases
almost equal the cost of a second wire. If it were desired to announce
the arrival of a train at any point of the line, at a level crossing, for
example, instead of an ordinary signal station, an apparatus might be
disposed at this point composed of a bobbin with a pivoted core termi-
nating in soft iron pallets oscillating between two magnets and carrying
a double arm bearing the words "train on line" and "line clear," one
or other of which would be shown at a suitable opening. When "train
on line" is shown it is accompanied by the ringing of a bell. The
batteries of the two posts in this case would also be similarly mounted
with regard to the commutator. It will be readily seen by examining
the latter that if the positive current of the departure battery brings the
pallet to the position "train on line" the return current from the
arrival station would be negative but in the reverse direction to the
former, and would attract the pallet in the same direction, thus leaving

page_text: the signal "train on line," while the current from the arrival station
on the arrival of the train will return the signal to "line clear," being a
positive current but in a contrary direction to the former. The man
at the level crossing is only required to wind up the bell striking
mechanism. This addition of an intermediate apparatus at the level
crossing involves no alteration whatever in the construction or operation
of the signal station apparatus.
The bell mechanism placed as above mentioned at intermediate points
in the circuit for indicating the presence of trains in the section and also
their direction is shown in Figures 9 and 10 of the Drawings, in which
a single apparatus serves for two or more directions. The part which
controls the bell mechanism is fixed on an axis A having a number
of rods G terminating in a pallet P fixed at an angle to the vertical
plane of the axis, said angle being regulated according to the degree of
motion to be imparted. Opposite each pallet is placed a bobbin E, the
soft iron core of which is prolonged at o, o', forming the poles of said
bobbin when a current passes through it; the core pivots on two screw
points, so that the pallets which are situate between two permanent
horse-shoe magnets F, F, may be moved from one to the other, according
to the direction of the current which traverses the bobbin; on the lower
prolongation o¹ is fixed a stem T, having a finger D jointed thereto and
provided with a signal disc V at its extreme end. By the oscillation of
the pallets between the magnets the finger is moved to and fro and
caused to act on the back of the inclined pallet P and moves it forward,
thereby oscillating the lever A and releasing the bell-striking mechanism;
by this movement the signal V is brought opposite an aperture in the
casing. The finger when nearly at the end of its course slips off the
inclined pallet, which being released therefrom is drawn back by its
spring R and arrests the bell mechanism. Thus if by a reverse current
acting on the bobbin the finger is returned to its original position, being
jointed, it will pass in front of the inclined pallet without moving the
lever A, and on returning it passes behind it, the signal being at same
time withdrawn from the aperture; thus according to the direction of
the current in the bobbin the finger will either move forward the inclined
pallet, and so release the bell mechanism, or pass in front of the same
without producing any effect on the mechanism.
It will be understood that whatever may be the number of the pallets
cach one when acted on will set the bell mechanism in action. In this

page_text: manner suppose the departure of a train be signalled at a signal station
by a station in correspondence therewith the intermediate bell apparatus
would be put in action and their signal discs be exhibited, and when the
arrival of the of the train is signalled by sending a current in the inverse
direction the intermediate signal discs would be withdrawn without the
bell mechanism being operated. It should be remarked that the negative
currents being in the opposite direction to the positive signalling currents
will act in the same manner as the latter on the bobbins and thus form
an additional guarantee of the proper working of the intermediate bell
mechanism.
By the foregoing arrangement the gate keeper will be warned of the
approach of a train at the time of its departure, and can tell by simply
inspecting the disc whether his section of the line is clear or not, and if
blocked in which direction the train is running.
Similar apparatus but of smaller size may be placed at junction
stations, for example, where the semaphores are required to be placed at
the point of junction. By suitably arranging the wires the signals
transmitted by the semaphores could be reproduced in these apparatus
so as to indicate the condition of all the lines leading to the station as
far as the corresponding semaphore posts in cach direction.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Melville Clark in the Great Seal Patent
Office on the 9th August 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex, a
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Tenth day of February, 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 successors, give and a
grant unto me, the said Alexander Melville Clark, Her special licence
that I, the said Alexander Melville Clark, my executors, administrators,
and assigns, or such others as I, the said Alexander Melville Clark,

page_text: ..
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, 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 SIGNALLING APPARATUS," a communication to me from abroad
by Paul Tesse, Henry Lartigue, and Pierre Désiré Prud'homme,
all of Paris, France, upon the condition (amongst others) that I, the
said Alexander Melville Clark, my exccutors 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 immediately after the date of the said Letters
3 Patent.
5
NOW KNOW YE, that I, the said Alexander Melville Clark, 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, reference being had to the two
Sheets of Drawings hereunto annexed, and to the letters and figures
marked thercon (that is to say):
This Invention relates to improved electric semaphore apparatus for
working either double lines of railway on the block system or single
lines.
In working double lines on the block system intervals of distance are
substituted for intervals of time, in order to keep two trains travelling
in the same direction at a safe distance apart. For this purpose the
line is divided into sections on which two trains are never allowed to
travel at one time. Moreover the sections cover each other to a certain
6 extent, besides which the commencement of each section, or in any case
the station is protected by signals placed at such a distance as to permit
of a train being stopped if the preceding train has not resumed its
journey.
An obstacle to the adoption of the block system when first introduced
was caused by the impossibility of signalling back to the commence-
ment of the section the arrival of a train at the other end, which is
however an essential condition. The application of electric-telegraphy

page_text: in working lines of railway affords means of accomplishing this object,
and this Invention relates to special apparatus to be employed for the
purpose which is also applicable to single lines. This apparatus
possesses the following advantages, viz., simplicity, absolute certainty
of the proper working of the signals, and perfect, connection between
the latter and the electric apparatus, which is actuated by the working
of the signals in such manner that the apparatus will indicate both
when a train enters upon and quits any section of the line in addition
in the case of single lines to showing whether the line is clear or blocked
by a train travelling in the opposite or the same direction.
This Invention is illustrated in the accompanying Drawings, Figures
1 and 2 of which show a front and side view of the electric apparatus.
A, cast-iron box, on the back plate of which are mounted all the
parts of the apparatus. Suitable holes are provided therein fitted with
brass bushes or bearings for the spindles. A strong iron plate is bolted:
to the box A, as shown in Figure 1, in dotted lines, similarly bored for
the spindles. X, iron spindle having a winch handle M at one end
and a crank arm B in line therewith at the other end, both being
exterior to box A. Spindle ✗ also carries, 1st, a tappet or finger D
placed at an angle to the hand lever M and crank B, as shown, and
2ndly, a snail-shaped cam C, the greatest developement or radius
of which is in the plane of the handle and crank B; 3rdly, a wood or
ebonite commutator O having seven projecting keys of silvered copper.
One of these keys T connects by means of a ring-shaped spring with
the spindle, the framing of the apparatus, and an earth wire. The six :
remaining keys a, a¹, b, b, c, c¹, are coupled together in pairs by
metallic connectors. At one side of the box is another spindle F on
which aro pivoted two arms fixed on the same boss at nearly a right
angle to one another. One arm J is a lever weighted at G resting
on cam C, a spring being interposed as a cushion to prevent shocks. a
The other arm R is in the same vertical plane with finger D, and is
provided at its lower end with a soft iron armature p attached by
a spring, as shown. Arm R is also provided with a slot U in which
works a pin forming part of a link, connecting said arm to a stop p
mounted to oscillate on a pivot. Opposite armature p is placed a a
Hughes' electro-magnet E composed of a permanent horse-shoe magnet,
the limbs of which are prolonged by soft iron cores, on which are placed
bobbins of covered wire.

page_text: -
-
There are four spring contacts around commutator O mounted on an
insulating plate N. Contact L' connects with the line wire L through
a paratonnerre or lightning guard Z, and contact E¹ with the bobbins of
the electro-magnet E and with the positive pole of the battery, while L
which is double connects with negative pole
At the upper part
of box A is placed a smaller Hughes' electro-magnet H connected
with magnet E, the bobbin on the north pole of the larger electro-
magnet, and the bobbin on the south pole of the smaller electro-magnet
being connected together and with the contact E¹ by a wire, while the
bobbin on the south pole of the larger electro-magnet, and that on the
north pole of the smaller electro-magnet are connected together and
with the earth wire T. Opposite clectro-magnet H is pivoted a bent
arm of brass carrying, 1st, a soft iron armature ƒ fixed by a spring
on a prismatic rod, and in contact with the poles of the electro-magnet;
2ndly, an arm Y also provided with a soft iron armature which, when
the armature ƒ is removed from the bobbins, comes into contact with
the limbs of the magnet, so that the latter may be always armed;
3rdly, a hammer and bell T; 4thly, a signal arm bearing the words.
signal received"
or other indication which is made to appear opposite
an opening in the front side of the box A. A spring Q tends to oscillate
the arm and remove armature ƒ from the poles of the electro-magnet
when the attraction of the latter is destroyed by the passage of a
negative current. A rod S provided with a regulating nut is screwed
into arm Y, its other end being slotted to receive a pin fixed on arm J,
thus connecting the latter with the above apparatus.
The apparatus of corresponding signal stations are connected together
two and two by a conducting wire.
The crank arm B before mentioned is connected by a rod with an arm
of the semaphore signal post. When the crank is in the upright position
shown the signal arm falls by its own weight, but by partly rotating
the winch handle M it is brought to an angle of 90 degrees to the
position it previously occupied, in which position the arm B is secured
by tappet D abutting against stop P, which prevents the further rotation
of spindle X. A pawl W holds the arm B in position and prevents its
moving in a backward direction. If by passing a positive current
through clectro-magnet E, the magnetism by which the pallet and
lever arm R were retained, be neutralized, the lever R and with it the
part J will oscillate on spindle I, stop P will be detached from tappet D,

page_text: and the latter being thus freed spindle X is enabled to complete a
revolution, and arm B is returned by the weight of the semaphore arm
to a vertical position. During the latter half revolution of the spindle
the cam C raises lever J, pallet fis again attracted by electro-magnet E,
and the stop P returns to position. During the first half revolution the
commutator has placed the line in communication with the pole of
the battery, which disengages the corresponding apparatus, while during
the latter half of the revolution a negative current is transmitted to
acknowledge receipt of the signal by striking bell T with hammer t and
exhibiting signal disc V. The armaturef is returned to contact with
the electro-magnet, and the hammer t at same time raised and signal V
moved out of sight, by the downward motion of lever J carrying with it
the rod S, which oscillates arm Y and stretches spring Q.
:
Figures 3, 4, 5, 6, and 7 show the arrangement of the semaphore
signal post, one of which is to be placed at both the sending and
receiving signal stations. The semaphore arms at the sending station
are in duplicate, one of small dimensions, colored white, and the other
which is larger being colored red, and provided with a red glass. The
two arms are placed at right angles. At the receiving station the
semaphore is also provided with two arms, the one being colored white
and of small dimensions, while the other has some special form, such as
an arrow for example, and of medium size. The "departure signal"
arm would be placed at the top of the post, and the "arrival signal" arm
at about mid height. A lamp is arranged to illuminate the red glass
when the red arm is horizontal, and the luminous rays may also pass
through a small opening in the arrow arm when it is horizontal.
The semaphore arms may occupy two positions at 90 degrees; in the
one case they hang down by their weight, and in the other they are
held in position by a rod or wire cord connected to the crank arm B of
the electric apparatus herein-before described.
The "departure signal" when set has the red arm placed horizontal,
and the white arm in the vertical position, while when unset the red arm
would hang vertically, and the white arm project horizontally.
re
The "arrival signal" when set has the white arm horizontal and the
"
arrow arm vertical, while when unset the white arm would hang
vertically and the "arrow arm be horizontal. The signal arms of the
two posts are thus symmetrical, and are both operated in the same way,
"

page_text: viz., set by hand and unset by electricity. S, semaphore signal post;
F, iron mounting for top of post; A, B, principal signal arms; a, b,
smaller signal arms; O, o, brakes and springs; T, pull rods of signal
arms A, B; t pull rods of smaller signal arms a, b; E, E, electric
apparatus described with reference to Figures 1 and 2 in position on the
signal post; K, gong; Q, q, radius links; L, lamp; ƒ,ƒ¹,ƒ³, Figure 4,
leuses; M, vertical reflector of lens f¹; R, r, reflector for illuminating
the lower part of the signal post S; G, guides of lamp holder P; p, c,
pulley and chain; J, counterweight.
It will be seen by reference to Figures 3 and 7 that the pivot of each
signal arm is provided with an angular iron plate or disc O, against the
flat side of which a spring bears when the arm has reached its maximum
degree of elevation, corresponding to an angle of 180 degrees, with the
crank arm B by which the signal is operated; said signal thus falls
slightly when the movement of the lever arm B is arrested at 200
degrees (by the tappet D, Figures 1 and 2, abutting against stop P), and
is retained in this position. The spring above mentioned acts as a kind
of brake in lowering the signal arms.
The illumination of the semaphore arms is effected by the aid of the
lamp above referred to, having three lenses, the lens f serving to
illuminate the glazed opening in the large arm A, disposed on the same
side as the lamp, the lens f¹ illuminates the glazed opening in the other
large signal arm B by means of a reflector suitably disposed. Beneath
this reflector is a second one of truncated conical form, inclined at such
an angle to the horizon as to reflect downwards a portion of the rays
from the lens f¹, while a third lens flights the foot of the post by
the aid of a reflector R, also of truncated conical form, placed at a
suitable angle. The dimensions of the various parts of the apparatus
may be varied according to circumstances, but the proportions shown
work well.
Figure 8 shows in outline a modified arrangement of signal post
adapted for single lines of railway, differing from the foregoing only as
regards the form and dimensions of the lower signal arms, and the mode
of operating the same. The engine driver whose attention is directed to
the signal arms on the left hand of the post will stop his train, either
when the larger signal arm is in a horizontal position to protect a train
only a short distance in front, travelling in the same direction, or when

page_text: the smaller signal arm is horizontal to block the line when a train is on
the line travelling in the opposite direction. Thus there can be no
liability of confusion in the signals, which are operated in an exactly
similar manner to those for a double line railway before described. In
this latter described arrangement a second lamp will be necessary for
lighting the lower signal arms.
From the foregoing it will thus be understood that by the combination
of the electric apparatus with the semaphores as described, the signalman
at the sending station will be assured that the current has passed
through the line with the desired effect of unsetting the semaphore
at the arrival station, inasmuch as the return current is absolutely
dependent on the lowering of the said semaphore signal arm. When
the train has reached the arrival station, the signalman at this point
turns the winch handle and resets the signal arm which returns to
white, and at same time transmits a current which disengages the
semaphore arm at the departure station, which in falling sets the white
arm at same time that a return current advises the arrival station that
its signal has been received. Thus all the working required (which is
exactly the same for the two signal posts) simply consists in giving half
a turn to the winch handle for announcing either the departure or the
arrival of a train. The signals are received without requiring any
intermediate agency, but are always accompanied by an audible signal,
either by sounding gong K in the case of a semaphore signal, or by
striking the bell T to acknowledge the receipt of signals at the corrc-
sponding station.
It is unnecessary to observe that each terminal station would be
provided with both a sending and receiving signal post, one for cach line,
or in the case of single line railways one for the up and one for the down
trains.
"
Each intermediate signal station would have a double apparatus, viz.,
four electric apparatus and four semaphore arms placed on the same
post, as shown in Figure 3, the two upper arms (right and left) being
red, and the two lower "arrow arms. In both arrangements one
battery or a single induction apparatus is sufficient, as also a single
gong, the use of the latter being to attract the attention of the signalman,
who by inspecting the semaphores will ascertain the origin of the signal.
Each apparatus is moreover entirely distinct from the others, and in the

page_text: arrangement which is preferred on account of its simplicity two wires
are necessary, one for the up trains and one for the down trains.
The apparatus may, however, be arranged for use with a single wire,
but in this case it would be necessary to use permanent magnets and to
reverse the currents, the greater cost of which would in some cases almost
equal the cost of a second wire. If it were desired to announce the
arrival of a.train at any point of the line (at a level crossing for example)
instead of an ordinary signal station, an apparatus might be disposed at
this point composed of a bobbin with a pivoted core terminating in soft
iron armatures oscillating between two magnets, and carrying a double
arm bearing the words "train on line" and "line clear," one or other of
which would be shown at a suitable opening. When "train on line." is
shown it is accompanied by the ringing of an alarum. The batteries of
the two posts in this case would also be similarly mounted with regard
to the commutator. It will be readily seen by examining the latter that
if the positive current of the sending battery brings the armature to the
position "train on line" the return current from the receiving station
would be negative, but in the reverse direction to the former, and would
attract the armature in the same direction, thus leaving the signal
"train on line," while the current from the receiving station on the
arrival of the train will return the signal to "line clear," being a positive
current, but in a contrary direction to the former. The man at the
level crossing is only required to wind up the alarum. This addition
of an intermediate apparatus at the level crossing involves no altera-
tion whatever in the construction or operation of the station signal
apparatus.
The bell mechanism placed as above mentioned at intermediate points
in the circuit for indicating the presence of trains in the section, and also
their direction of motion is shown in Figures 9 and 10 of the Drawings,
in which a single apparatus serves for two or more directions. The part
which controls the bell mechanism is fixed on an axis A having a
number of rods G, terminating in a steel pallet P, fixed at an angle of
10° or 15° to the vertical plane of the axis, said angle being regulated
according to the degree of motion to be imparted to the axis. Opposite
cach armature is placed a bobbin E, the soft iron core of which is pro-
longed at o, o¹, forming the poles of said bobbin when a current passes
through it. The core pivots on two screw points so that the armatures
which aro situated between two permanent horse-shoe magnets F, F',

page_text: :
may be moved from one to the other, according to the direction of the
current which traverses the bobbin. On the lower prolongation o¹ is
fixed a stem T having a finger jointed thereto, and provided with a rod
carrying a signal disc V at its extreme end. By the oscillation of the
armatures between the magnets the finger is moved to and fro and
caused to act on the back of the inclined pallet P, and moves it forward,
thereby oscillating the lever A and releasing the bell striking mechanism.
By this movement the signal arm V is brought opposite an aperture in
the casing. The finger when nearly at the end of its course slips off the
inclined pallet which being released therefrom is drawn back by its
spring R, and arrests the bell mechanism. Thus if by a reverse current
acting on the bobbin the finger is returned to its original position, being
jointed, it will pass in front of the inclined pallet without moving the
lever A, and on returning it passes behind it, the signal being at same
time withdrawn from the aperture. In this manner according to the
direction of the current in the bobbin the finger will either move forward
the inclined pallet and so release the bell mechanism, or pass in front of
the same without producing any effect on the said mechanism.
It will be understood that whatever may be the number of the pallets
each one when acted on will set the bell mechanism in action. Thus,
suppose the departure of a train be signalled at a station by a station in
correspondence therewith the intermediate bell apparatus would be put
in action and their signal discs be exhibited, and when the arrival of the
train is signalled by sending a current in the inverse direction the inter-
mediate signal discs would be withdrawn without the bell mechanism
being operated. It should be remarked that the negative currents
announcing the receipt of a signal being in the opposite direction to the
positive signalling currents will act in the same manner as the latter on
the bobbins, and thus form an additional guarantee of the proper working
of the intermediate bell mechanism.
By the foregoing arrangement the gatekeeper will be warned of the
approach of a train at the time of its departure, and can tell by simply
inspecting the disc whether his section of the line is clear or not, and if
blocked in which direction the train is running.
Similar apparatus but of smaller size may be placed at junction a
stations, for example where the semaphores are required to be placed at
the point of junction. By suitably arranging the wires the signals trans-

page_text: mitted by the semaphores could be reproduced in these apparatus so as
to indicate the positions of all the lines leading to the station as far as the
corresponding semaphore posts in each direction.
The principal advantages of the herein-before described system of
railway signalling may be thus stated.
The trains are protected in rear and signalled to the next station
ahead, and also if desired to intermediate points by one and the same
operation.
The signal protecting the train after starting is set by hand, and
under the eyes of the person giving the signal.
The electric apparatus is so connected with the semaphore mechanism
that the former are operated by the working of the latter, and there can
consequently be no false security imparted should the current become
unexpectedly interrupted; on the other hand the signalman is not
required to mechanically reproduce the signal received by a distinct
electrical apparatus, such office being performed by the receiving appa-
ratus without the assistance and even in the absence of the signalman.
All signals are announced by a gong.
There is an immediate check on a signal transmitted by the apparatus
itself which is operated electrically so that the signalman transmitting
a current is assured that it has reached and produced the desired effect.
The electrical apparatus employed are those having the least
complicated elements, and consist merely of an ordinary electro-magnet
with its armature and a commutator.
The semaphore apparatus is also very simple and acts by gravity
alone. The apparatus being divided into distinct groups, any disarrange-
ment may thus be localised which much facilitates an examination in
case repairs are needed. Even in case the electric apparatus should
cease working the security of the trains remains the same, inasmuch as
the signals covering said trains are set by hand without the aid of
electricity, there can consequently be no mistakes made through the
absence of an clectric signal, the trains at most being required to make
a momentary stoppage or preferably slowed, and driven with caution to
the next signal post which will indicate to the driver whether he should
still proceed slowly or resume his ordinary rate of travelling. The
arrangements herein-before described are those which have been deemed
B

page_text: the most practical and most adapted to those of apparatus in present
use, but it will be understood that both the form and dimensions of
the various parts of the apparatus may be varied, that the electric
apparatus employed may consist either of a battery or induction
apparatus, that one or two wires may be used, and consequently either
simple electro-magnets or electro-magnets combined with permanent
magnets, and that the lowering of the signals may be produced by
reducing the power of the magnet by passing a reverse current through
coils attached to its poles, as in the Hughes' printing telegraph apparatus.
Figure 11 shows an arrangement in which the armature a of a Huglies'
electro-magnet b, instead of being carried by the lever on which the
magnet acts, is mounted on a flat spring c fixed to said lever d in such
manner that the primary effect of reducing the magnetism by passing
a current through the coils, is to permit of armature a being sharply.
detached by the elasticity of the spring c, although the motion of lever d
be but slowly. executed. Thus a current however momentary will
always produce the desired effect which is to detach the armature
sufficiently to prevent the magnetism (which resumes its action after the
passage of the current) from again attracting and retaining the armature
before the lever has performed its movement.
I
Figure 12 shows an arrangement by which the balance weight e for
holding the lamp of a semaphore signal or disc in position instead of
being permanently attached to the chain f, and thus raised when the
lamp is lowered, and vice versa, is suspended on a lever o terminated by a
hook which is connected to the chain when the lamp is in position. 1
In this manner the weight acts on the chain and holds it in tension
the same as if it were permanently attached thereto, while there is less
chance of the chain becoming broken, and accidents due to the fall of
the weight from such causes are entirely avoided.
Figure 13 shows an arrangement of two or more Hughes' magnets by.
means of which successive currents passed in contrary directions may be
made to turn a spindle in one direction with the aid of a weight or
spring, said arrangement being analogous to that herein-before described
and illustrated in the Drawings. A. is the spindle, which has a tendency.
to turn in the direction of the arrow, and is provided with a tappet Da
and double cam C, C¹. On the right and left are two centres M, M',
carrying arms R, J; R', J¹, bent at less than a right angle, and

page_text: disposed as shown. The vertical arms R, R¹, each carry soft iron
armatures P, P¹, and are jointed to oscillating stops B, B¹, against which
tappet D of spindle A abuts for stopping the motion of the latter. By
removing the stop the spindle is enabled to make a half turn, when
finger D abuts against a second stop B¹. Two Hughes' magnets E, E¹,
are placed opposite armatures P, P', and with which the latter are
usually in contact for holding the bent arms and stops in position.
These magnets are disposed in such manner that the current which
weakens the one reinforces the other, the first releasing its armature
and enabling the part R, J, to oscillate on its pivot M, and remove the
stop B, while the second retains its armature. The two electro-magnets
being in the circuit of the samo wire it will be understood that by
passing positive and negative currents in succession, first one and then
the other armature and stop may be actuated for rotating spindle A.
At each semi-revolution of the spindle the cams C, C¹, raise one or other.
of the horizontal arms J, J', which in falling detach the armatures, and
thereby reconnect the latter with their electro-magnets.
This arrangement in a modified form may also be employed in con-
nection with the improved electric semaphore apparatus of this Invention
in the following manner:-Spindle A is provided with double signal
arms, which are exhibited according to the current passed through
the coils interposed in the circuit of the semaphore apparatus to show
either "line clear "
or "train on line," and the direction in which it is
travelling.
Several of these apparatus may be connected according to the number
of lines provided with a single alarum, from which power would be
obtained for turning spindles A. This arrangement would be substituted
for the alarum herein-before described at intermediate points of the.
sections and at junctions..
The apparatus of this Invention may also be applied for working
distance signals, whether operated directly thereby or independently by
connecting a lever with the wire by which the motion is transmitted,
as shown in Figure 14. In this case when the disc is turned to
danger" by means of the lever it may be returned to position by the
signalman, but if on the contrary it is set at "danger" by means of the
electric apparatus, the assistance of the current of the corresponding
signal station is indispensable for changing its position. For example,
$6

page_text: let A be the electric apparatus connected with signal disc B by a wire
cord C passing round pullies D; E is a lever interposed in the wire, by
bringing which into the notch F, Figure 15, of quadrant G, the disc will
be turned and held at "danger," the disc being returned to position by
bringing back the lever, this being useful to protect trains in shunting
at stations. If, on the contrary, it is desired to cover a train on the
line the crank of apparatus A is turned for moving lever E, which in
this case slides over the notch F without entering, and so sets the disc
at "danger," the position of the latter being altered only by releasing
the tappet of the electric apparatus, Figure 13, from the stop with the
aid of an electric current from the corresponding signal station. This
arrangement may be applied to all disc signals operated by balance
weights

page_text: 4thly. I claim the audible signal apparatus operated by the falling of
the semaphore arms, as shown and described.
5thly. I claim the bell mechanism for intermediate points and
stations, arranged as shown and described.
6thly. I claim the arrangement of lamp and reflectors for illuminating
the signal posts, as shown and described.
In witness whereof, I, the said Alexander Melville Clark, have
hereunto set my hand and seal, this Ninth day of August, in
the year of our Lord One thousand eight hundred and seventy-
three.