Improvements in or connected with Railway Signals.
Year: 1893

page_text: Date of Application, 28th Mar., 1893
Complete Specification Left, 28th Dec., 1893-Accepted, 3rd Feb., 1894
PROVISIONAL SPECIFICATION.
Improvements in or connected with Railway Signals.
1, GEORGE CARRINGTON PURVIS of 43, Barclay Place, Edinburgh, Scotland,
Doctor of Medicine and Bachelor of Science, do hereby declare the nature of
this invention to be as follows:-
The invention consists in dividing the railway track (or tracks) into separate
portions or sections which are electrically disconnected from each other; in
addition the rails of each section are also electrically disconnected (insulated)
from the earth and from each other (by the 4 foot way or space between the rails)
as far as possible. The length of each section will depend partly on (1) the
distance of the existing signal boxes & their signals from each other and partly
on (2) the amount of insulation to which the rails can be subjected, the better the
insulation the greater may be the length of the section and the further apart the
signal boxes and signals from each other. The rails of each section or circuit are
connected at their commencement or proximal ends with the poles of a battery
or other furnisher of electricity (placed preferably inside the signal box
which stands at or near the head or commencement of each section or circuit) by
means of conducting wires, so that the rails of cach section, the conducting wires,
& the battery form an open circuit, the circuit has a second gap or break (the first
gap being the space between the rails i.e. the 4 foot way) in one or other of the
conducting wires; this gap which should not exceed a few inches in extent can
however be filled up, and the electrical continuity of the conducting wire be
thereby established, by means of a metallic bar or contact piece (of copper by
preference) which is firmly attached to the lever in the signal box which works the
ordinary signal outside, the contact piece is attached to the lever not directly
(i.e. metallically) but through the medium or intervention of a piece of wood or
some other badly conducting substance and is so arranged that when the signal is
at "danger" the contact piece is withdrawn from the gap, but when the signal is
at "line clear" the contact piece completely fills up the gap in the conducting wire.
Next, I attach to the portion of the circuit within the signal box an ordinary
vibrating (magneto-electric) bell-alarum which will ring the whole time the circuit
is closed and the current is passing. For the passage of this current two conditions
must be fulfilled; viz. :-(i) the signal must be at "line clear" and (ii) the dis-
continuity or break in the circuit between the rails must be abolished, the latter
occurs when a train, or engine, or carriage, or truck, with metallic wheels and axles,
is on that section of the track which the signal (in its rear) should normally
protect but does not do so as it is by supposition standing at "line clear," the alarm
is therefore set ringing inside the signal box and the signalman is warned of the
fact that his signal is at "line clear" when there is a train ahead which his signal
should cover, he has then only to put up his signal to "danger" when he not only
breaks the circuit and thus silences the alarm but thereby also prevents a collision
with a succeeding train on the same track. To further minimise the risk of collision
a tell-tale arrangement may be placed outside the signal box but connected with
the circuit and actuated magneto-electrically, such an arrangement for instance as
the raising of an arm (during daylight) and the exposing of a danger light (during
darkness) and which comes into action only when the current is passing, or in other
words when the signalman fails to do his duty.
Dated this 27th day of March 1803

page_text: Improvements in or connected with Railway Signals.
I, GEORGE CARRINGTON PURVIS, of 43 Barclay Place, Edinburgh, in the
County of Midlothian, North Britain, Doctor of Medicine, 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 :-
This invention relates to improvements in or connected with railway signals and
has for its object to minimise the risk of a collision taking place between two
trains.
In carrying out my said invention, as is shown in the accompanying diagram, I
divide the track or tracks into separate portions or sections, such as sections 1, 2
and 3; said sections being electrically disconnected or insulated from each other
by any suitable means.
The rails A of each section are also disconnected or insulated from the earth and
from each other by the four foot way or space between the rails having the
ordinary wooden sleepers.
The length of each of the said sections will depend on the distance of the signal
boxes and their signals from each other and on the amount of insulation to which
the rails are subjected, as the better the insulation is, the greater the length of the
section and the further apart of the signal boxes and signals may be.
The rails of each of the said sections may be insulated from each other so as to
disconnect or break the electrical continuity of the sections by insulating the fish
plates from the rails through the medium of india-rubber or other non-conducting
material which may be placed along the parts of the rails and the fish plates which
come in contact with each other.
Or if desired the disconnection of the rails may be accomplished by removing
the fish plates and employing longitudinally placed wooden sleepers, braced by
cross sleepers, the extremities of each section of rails being fixed on chairs or
otherwise secured to the sleepers.
Or the disconnection may be effected also by removing the fish plates and
closely approximating the ordinary transverse wooden sleepers, on each side of
the disconnection, in such a manner that the ends of each section are as nearly
as possible supported by the, chairs. The rails of each section are connected at
their commencement or primeval ends with the poles of a battery B, or other
furnisher of electricity, which is preferably placed inside the signal box for the
said section, by means of conducting wires C, C', in such a manner that the
rails, conducting wires C, C', and battery B form an open circuit for each section.
The said open circuit is provided with a small gap or break within the signal
box, which can be filled up when desired by the signalman actuating the signal
lever E and so causing the lever to force a metallic bar or contact maker F
into position as shown in sections 2 and 3, and in which the signals G are
standing as for "line or track clear" thus establishing the electrical continuity
of the conducting wires C, C¹. The metallic bar F, which is preferably made
of copper, is suitably secured to the signal lever E through the medium or
intervention of a piece of wood or other badly conducting substance or material,
in such a manner, that when the signal G (which may be either a home or
distant though preferably a distant signal) stands at "danger" the bar or contact
maker F is withdrawn from the wires C, C², so as to break the circuit, as shown in
section 1; but on the signal G standing at "line clear" the bar or contact
maker F will be in the position shown in sections 2 and 3.
Each section of the track is provided with an ordinary vibrating, magneto-electric
bell alarum or alarm H mounted within the signal box and suitably connected to
the circuit wire C₁ or wire C, in such a manner that during the time the circuit is

page_text: complete and the current passing the alarm H will ring. The said completion of
the circuit being effected when two following conditions take place, that is to say
when the signal G is at "line clear" and the break or discontinuity of the circuit
between the rails A is abolished, this latter condition occurring when a train, engine,
carriage, van or truck having metallic wheels and axles, is on the section which
the sigual, at the rear of the same, should normally cover, but does not do so, as it
is standing at "line clear" as shown in section 3. When the foregoing conditions
are fulfilled the alarm H will ring and so warn the signalman that the signal G is
at "line clear" when it should be at "danger" owing to the fact of a train J being
on the track which the signal should cover; when this is the case, the signalman
operates his lever E so as to put up his signal G, to "danger" and at the same
time the lever E withdraws the contact piece F from the wires C, C₁, and by so
doing breaks the current and circuit and silences or stops the ringing of the
alarm H, thus preventing the liability of a collision taking place on the saine section
of the track.
At X a branch line is shown entering the main line.
"
The accompanying drawings shows the following example:-Section 1 is
"blocked" with its signal G at "danger" so as to cover the train J' which is
passing along the track in the direction of the arrows K. Section 2 is "open
with its signal at "line clear;" and section 3 shows a mistake on the signalman's
part in not having put up his signal to "danger" so as to cover the train J which
has passed the said signal, this mistake being pointed out to the signalman by the
ringing the alarm until he puts his signal to "danger."
If desired to further minimise the risk of a collision taking place, I
may provide
a tell-tale arrangement outside the signal box, but connected with the circuit and
electrically actuated by one or more electro-magnets the said tell-tale arrangement
may consist of a light arm capable of being raised, lowered or rotated during
daylight and exposing a "line clear
66
or danger" light during darkness. The
said tell-tale arrangement coming into action when the circuit is complete, that is
to say, when indicating "danger" or in other words when the signalman fails to do
his duty.
In circumstances where sufficient insulation cannot be obtained suitable insulated
conductors may be employed and placed alongside the rails so that the flanges of
the wheels come in contact with the said conductors. Or the rails themselves may
be more perfectly insulated by placing any suitable non-conducting material between
the rails and chairs by means of which direct electrical continuity between the rails
and the chairs is obviated.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1st. The general arrangement and combination of parts, constituting my improve-
ments is safe signalling for railways for the purpose of preventing a collision,
substantially as herein before described and shown in the accompanying diagram.
2nd. The break or gap in one or other of the conducting wires C, or C¹ whereby
the circuit or current is completed or closed when a train is on the section and the
signal at "line clear" whereby an alarm is given, substantially as described and
shown in the accompanying diagram.
Dated this 27th day of December 1893.
JOHNSONS,
115, St. Vincent Street, Glasgow, Applicant's Agents.