Year: 1886

page_text: I CHARLES WILLIAM PRIDHAM of 10 Cromwell Crescent, West Cromwell Road
in the County of Middlesex Physician do hereby declare the nature of this invention;
and in what manner the same is to be performed to be particularly described and;
ascertained in and by the following statement:-
The object of my invention is to enable an operator at a station or in a signal
cabin to transmit telegraphic signals to the driver of a train especially such signals'
as are required to instruct the driver whether to stop or to proceed.
The method which I prefer involves the use of two line wires but as hereinafter
explained my invention may be practiced with one line wire.
On the train I provide a small semaphore arm or signal so connected with the
armature of an electro-magnet that when, the armature is attracted the signal arın
is moved to the "safety
<
or 'go on "position.
"
When the signal arm is in the safety position a latch retains it. The latch also
is under the control of another electro-magnet and is lifted by it when not required
to operate.
These electro-magnets are included in two separate circuits and work quite
independently the one of the other.
The circuits are closed by contact makers on the train coming against contact
posts provided on the line of railway.
When I employ two line wires I provide also a key or keys in the signal cabin
by means of which I can connect either one or other of the line wires with a
battery.
Each circuit when complete may be traced from the battery at the signal cabin
by the line wire to a contact post, thence by the contact maker on the train to one
or other of the electro magnets, thence to the wheels of the train and finally by the
rails and earth back to the battery.
go on
"
•
When one circuit is completed in this manner the signal arm is moved to the
or "safety" position and there it becomes latched. When the other
circuit is similarly completed the latch is lifted and the signal arm passes to the
danger position.
In each circuit I introduce a bell to sound when the circuit is complete. I use
bells of different pitch.
To facilitate signalling at night the frame of the instrument is perforated with
an aperture behind which a light is placed. The semaphore arm also carries a disc

page_text: of red glass and when it is in the "danger" position the glass comes in front of
the light which is then seen, red. By providing a receiving instrument in the
signal cabin and a speaking key upon the train communication between the train
and the signal cabin may be established when the train is standing at a post.
An obvious modification applicable to the electric semaphore instrument on the
train is that the electro-magnet should be arranged to put the signal arm to the
danger" position, whilst the lifting of the latch allows it to pass to the safety
position.
**
•
.
When I wish to work with one line wire only the arrangement is similar but the
battery which places the signal arm in the "danger" or "stop" position is carried
.either on the train or on the line near to the contact post and acts under all cir-
cumstances on a train passing the post this danger signal being taken off if not
required, by the line current when the next post is passed.
In order that my said invention may be fully understood and readily carried
into effect I will proceed to describe the drawings hereunto annexed.
Figure 1 is a diagram of the arrangements on the line of railway.
Figure 2 is a front view and Figure 3 is a back view of the instrument which
I provide upon the train.
a is one line wire and b is the other line wire, these may be carried on posts and
insulators along the line of railway in the usual manner. The wire a is connected
at intervals with the insulated contact posts c and the other line wire b is similarly
connected with the insulated contact posts d-f and g are finger keys in the signal
cabin and is a galvanic battery connected by one pole to earth and by the other
to the finger keys. By pegging down either finger key the corresponding row of
contact posts is connected with the battery through the line wire but the circuit is
not completed until a train passes one of the posts. It is not necessary to employ
two keys a switch may be made to serve the purpose.
"
The instrument on the train contains an electro magnet i and j is its armature;
the armature is moveable about a fulcrum at j¹ and has an arm j. j³ is a spring
which draws back the armature from the magnet. The upper end of the arm j² is
loosely pin jointed to a disc ¹ on an axis k. On the axis k is fixed the signal
arm l
When the armature j is attracted the signal arm is raised to an upwardly
inclined. position which is the "safety or "go on" signal. m is a latch lever, it
has its fulcrum at m¹ and carries a pin at m². When the signal arm reaches the
safety position the pin m² drops into a notch * in the disc k¹ and retains the
Bignal arm. m³ is an armature on the latch lever m and n is an electro magnet
which sometimes attracts this armature; when it does so the latch is lifted and
the signal arm then falls to the " danger" or "stop" position in which it is repre-
sented in Figure 2. In the same circuit with the clectro magnet i there is an
electric bello and in the circuit of the electro magnet n there is another similar
electric bell which however is not represented in the drawings. The two bells
have different sounds. The coils of the electro magnet i are connected at one end
with a contact maker carried on the train and at the other with the bell coil and
through this with the axle and wheels of the train. The coils of the electro
magnet n are similarly connected with another contact inaker and another bell.
The action is as follows:-when the key f'is pegged down the battery his
connected by the line wire a with the contact posts c and when the corresponding
contact maker on the train comes against either of these posts the current passes
through the coils of the electro magnet i and the bell o. The signal arm if not
previously in the "safety" position is then brought to it by the action of the
magnet and it is latched in this position. The safety bello also sounds and it does
80 as the train passes every post c until the finger key f is released and instead
of it the finger g is pegged down. Now the line wire b and the posts d are

page_text: connected with the battery and when the corresponding contact maker on the
train comes against a post d the battery circuit is completed the latch pin m³ is
lifted and the signal arm being released it drops to the danger. position-the
danger bell will also' ring. The driver of the train will now stop as quickly as he
can upon a post c; his signal will continue to stand at the danger or "stop'
position until the signalman in the cabin by pegging down the key f gives the
"safety" or "go on" signal..
נו
To facilitate the use of the apparatus at night I insert a red glass: into the end
of the signal arm Z. When the arm is in the "danger" position the glass covers
an aperture o in the foundation plate of the instrument behind which a light is
placed. A red light is consequently seen as the danger signal and a white light to
indicate safety.
For contact posts and the contact makers on the train I prefer to employ
an iron bar hung horizontally beneath one of the carriages of the train by
spiral springs and iron chains. The springs support the bar normally and the
chains prevent the springs being overstretched or broken. The bar may be about
12 feet long and turned upwards somewhat at its ends. The contact post may be
of cast iron and have a globular head; the head is insulated and is connected with
the line wire.
If I desire to establish speaking communication between the train and the signal
cabin I provide a speaking key upon the train to open instantaneously the other-
wise closed circuit and at the signal cabin I interpose a receiving instrument
between the keys and the battery. When it is required to communicate in this
way the train is brought to rest at a post through which the circuit is closed.
"
Figure 4 is a diagram showing the modification which I make when using but
one line wire. I apply a battery at every post or I carry a battery in the train in
the circuit of the magnet n; in either case the signal arm 1, passes to the "danger
or "stop" position whenever the train passes a post d and the signal is taken down
again when the train passes the next post c. When this method is employed it is
convenient that the interval between these posts should be short.
It is not essential to this arrangement that the signal arm should be placed in
the "danger." position by electrical means; for example it may obviously be done
mechanically or pneumatically or otherwise by the movement imparted to a contact
bar on striking a post.
I prefer however the arrangement with two line wires as being simpler and less
likely to be deranged or to mislead.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is :-
1. The combination of apparatus for train signalling consisting of the following
parts at the signal cabin, a battery and a key for applying the battery to one or
other of two line wires; on the line, the said insulated line wires and two sets of
insulated contact posts connected therewith; and on the train contact bars making
contact with the posts; a signal arm and two electro magnets with armatures one
operating to move the signal arm to a position in which it becomes latched and
the other to release the signal arm by moving the latch all so connected as to
operate substantially as described.
2. The combination with the apparatus set forth in the preceding claiming
clause of a key upon the train and a receiving instrument in the signal cabin by
which when the train is stopped at a post an operator on the train can com-
municate with the signalman substantially as described.
3. The combination of apparatus for train signalling consisting of the following
parts at the signal cabin, a battery and a key for applying the battery to a line
wire; on the line the said insulated line wire and insulated contact posts con-
nected therewith; on the train, a signal arm an electro magnet and an armature
which when attracted causes the signal arm to assume the "safety" or "go on"
"

page_text: position and finally other independent mechanism operating at other times to place
the signal arm at the "danger" position all substantially as described.
4. In an electric semaphore signalling apparatus adapted to be carried on a train,
the aperture o through which a light is shown and the coloured glass l¹ in the
semaphore arm which shades this aperture when the arm is in the danger position
substantially as described.
5. My improved signalling apparatus substantially, as described in respect to
Figures 1, 2 and 3 of the annexed drawings.