IMPROVE- •MENTS IN RAILWAY SIGNALLING APPARATUS
Year: 1885

page_text: I, HARRY LOUIS DAVIS of the Engineers' Department, Great Eastern Railway,
Liverpool Street, in the City of London, Associate Member of the Institution of
Civil Engineers, do hereby declare the nature of said invention for "IMPROVE-
•MENTS IN RAILWAY SIGNALLING APPARATUS" to be as follows:-
Where lines of railway cross one another, as for example at junctions, stations,
crossings on the level, it is usual to provide interlocking signals, the object being to
preclude the possibility of giving the safety signal for a train to pass along either
line when the points are not in the proper position for that purpose. The inter-
locking gear, however, is usually applied in the signal cabin or at some point
intermediate between the place at which the operating levers are situated and that
part of the rod immediately connected to the semaphore arm or other signalling
device. Also, semaphore arms and other signalling devices are commonly so
arranged that in the event of fracture in the connecting rods or wires they may
automatically assume the danger attitude. In practice, however, should a fracture
or disconnection occur at a considerable distance from the semaphore arm or
signalling device it may be prevented from assuming the danger attitude by the
restraining action of the weight or friction of the rod or wire connected to it.
Now, the object of this invention is to preclude the lowering of a signal for a
train to pass along one line unless and until not only the points but also the signals
of conflicting lines are in the proper positions for that purpose.
To this end the semaphore arms or signalling devices are themselves directly
locked by mechanical means acting upon the arms or signalling devices themselves
and arranged in such a way that in the event of fracture of the connections, the
lowering of a signal for a train to pass cannot be effected whilst another semaphore
arm or signalling device is in a conflicting attitude.
An arrangement of apparatus for this purpose, which for the sake of explanation
I will assume to be applied at a junction of a branch line with a main line, is as
follows:-
Upon the signal post I provide a locking device so situated as to engage with
the pin whereby the semaphore arm or its equivalent is connected to its operating
rod when the semaphore arm or its equivalent is in the danger attitude. The
arrangement is such, however, that when the semaphore arm or its equivalent is in

page_text: any other attitude than that representing danger the locking device cannot be
moved into the position corresponding to the locked condition of the semaphore
arm or its equivalent.
The rod or wire whereby the locking device is operated is itself connected in
some convenient way with and worked by the lever used to lower the conflicting
signal. Thus, it will be understood, that if, for example, the signal of the branch
line be lowered and remain so after the moving over of its lever, then the signal of
that part of the main line which is crossed by the branch line cannot be lowered,
because the moving over of the lever to lower it will be prevented by the locking
device of the branch line, which as already stated, cannot be moved over unless and
until its semaphore arm or equivalent is in the danger attitude.
It is to be noted that apparatus to operate on the principle of this invention may
be constructed in various forms and applied in a variety of situations and also that
the locking device instead of being arranged to engage with the pin whereby the
semaphore arm or its equivalent is connected to its operating rod may be caused to
engage with some other part or projection so long as the arrangement be such that
in the event of failure of the one signal to return at the proper time to the danger
attitude, the other signal shall be prevented from being lowered into the safety
attitude and that the locking device shall act directly upon the semaphore arm or
other signalling device itself as distinguished from the locking contrivances which
act upon the rods or wires that are used to operate the semaphore arms or their
equivalents.

page_text: Improvements in Railway Signalling Apparatus.
I, HARRY LOUIS DAVIS, of the Engineers' Department, Great Eastern Railway,
Liverpool Street in the City of London, Associate Member of the Institution of
Civil Engineers, 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 :-
Where lines of railway cross one another, as, for example, at junctions, stations,
crossings on the level, it is usual to provide interlocking signals, the object being
to preclude the possibility of giving the safety signal for a train to pass along either
line when the points are not in the proper position for that purpose. The inter-
locking gear, however, is usually applied in the signal cabin or at some point
intermediate between the place at which the operating levers are situated and that
part of the rod immediately connected to the semaphore arm or other signalling
device. Also, semaphore arms and other signalling devices are commonly so
arranged that in the event of fracture in the connecting rods or wires, they may
automatically assume the "danger" attitude. In practice, however, should a
fracture or disconnection occur at a considerable distance from the semaphore arm
or signalling device it may be prevented from assuming the "danger", attitude by
the restraining action of the weight or friction of the rod or wire connected to it.
Now, the object of this invention is to preclude the lowering of a signal for a
train to pass along one line unless and until not only the points but also the signals
of conflicting lines are in the proper positions for that purpose. To this end the
semaphore arms or signalling devices are themselves directly locked by mechanical
means acting upon the arms or signalling devices themselves and arranged in such
a way that in the event of fracture of the connections, the lowering of a signal for
a train to pass cannot be effected whilst another semaphore arm or signalling
device is in a conflicting attitude.
44
Fig. 1 of the accompanying drawings is a diagram plan of a junction illustrating
the application of my invention. S is the signal cabin containing the working
levers which are connected to the several points and signals. These levers are
usually interlocked with each other within the cabin so that no lever can be moved
which would move a point or a signal in conflict with some other point or signal.
It may happen however that, through fracture or derangement of some of the
connections from the levers to the signals, especially when the connections extend
over considerable distances, a 'safety" signal is displayed when it should not be
shewn. For example, assuming that the signal A is lowered as indicated in Fig. 1,
inviting a train to pass from the up branch U B to the up main line U M, then if
at the same time the signal B should be lowered inviting a train to pass along the
down main line D M, there might occur a disastrous collision of the trains at the
place C where the two lines cross each other. In order to avoid the possibility of
such antagonism of signals, I lead from the cabin S not only the usual connections a
and b for working the signals, but also separate connections, indicated respectively
by the dotted lines a and b which effect locking of the signals at the signals
themselves in the manner shewn in Fig. 2 which is a front view of the upper part
of the signal post and the semaphore arın. The ordinary rod D which works the

page_text: .
signal is connected to the crank pin e of the semaphore arm. E in the usual way.
The locking rod F is jointed to a bell crank lever Ġ the upright arm of which is
made as a hook catching over the upper end of the rod D. Unless by the movement
of the locking rod F the bell crank G is brought to the dotted position G' when its
hooked end is withdrawn, the rod D cannot ascend and consequently the semaphore
arm E cannot descend to indicate safety.
In many cases, especially when the signals to be interlocked are near each other,
instead of extending locking rods from each to the signal cabin, a locking rod may
be connected from the one signal to the other as shewn in Fig. 3, which a front
view of two neighbouring signals H and K thus interlocked.. The signal H is
locked in the same way as the signal E in Fig. 2 by the hook ended lever G, but
the rod F which works this lever is extended across to a bell crank lever L which
is linked to the semaphore K. When this signal is down as shown, the other
signal H cannot be lowered because its rod D is held down by the hook of G. Now
when K is raised to the "danger" attitude the lever G is moved withdrawing its
hook from D, and consequently H can be lowered. When H is lowered, as the
hook end of G is now stopped against the side of the rod D, G cannot be moved
back to its locking attitude, consequently the rod F and bell crank L are held
stationary and K cannot be lowered. Obviously, instead of a simple rod F
extending from post to post there might be a set of connected rods carried down
the one post, along the ground and up the other post to effect interlocking of two
signals in the manner described. Thus instead of connecting the sets of locking
rods a¹ and b¹ of the signals A and B as shewn in Fig. 1 each to the working rod b
and a of the other signals, these rods may be connected to the interlocking gear of
the levers in the cabin S and may there be interlocked in the usual way with such
of the point and signal levers as should be subject to the control of the signals A
and B. For example, when the signal A is lowered, the points P should have been
set right for passage of a train from the up branch UB to the up main line Ụ M,
and as long as the signal A 'remains down, these points should not be capable of
being shifted. In order to ensure this, it is only necessary to connect the locking
rod a to the interlocking apparatus in the cabin S in such a way as to lock the
lever which moves the points P when it has set the points right for the up branch,
and in a similar way locking rods such as a¹ and b¹ which are directly connected
from the semaphore arms may be interlocked with any of the levers in the cabin S,
thus ensuring safety even if the connections a and b which work the semaphores
should be fractured or deranged.
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
"
In railway signalling apparatus, providing for and immediately at a semaphore
or like signal a lock worked by another signal or by its operating lever or rod in
such a manner that when either of the two signals is moved to indicate "safety
the other locked in the attitude indicating "danger," substantially as and for the
purpose herein set forth.