Improvements in Interlocking the Signals with the Switches on Railways.
Year: 1891

page_text: Date of Application, 20th Feb., 1891
Complete Specification Left, 20th Nov., 1891-Accepted, 19th Mar., 1892
PROVISIONAL SPECIFICATION.
Improvements in Interlocking the Signals with the Switches on
Railways.
1 CUTHBERT ELLISON CARR, of Hedgeley, Alnwick, in the County of
Northumberland, Engineer, do hereby declare the nature of this invention to be
as follows:--
My present invention relates to interlocking the signal handles with the
tongues" of the switches by apparatus alternative to and, in certain cases,
preferable to that described in my Specifications of Patents Nos. 15,077 dated
Sept. 24 1889 and 6859 dated May 3rd 1890.
In order to ensure that the signalman shall, in every case, know if any pair of
switches has failed to act perfectly, the handles for operating the signals which are
dependent upon such switches are interlocked with the tongues of the switches by
apparatus alternative to the rods and cranks leading from the switches to the signal
cabin, as described and shewn in the before named Specifications, which are
replaced by the fluid itself.
This apparatus consists of two cylinders, preferably placed in or near the signal
cabin, and will assume that the locking is effected by slotted sliding plates
controlling the passage, through their slots, of notched rods connected with the
signal handles as in my Specification No. 68599.
Each cylinder in the cabin is connected with the cylinder or cylinders at the
switches by a pipe.
The operations are as follows ei. :-
The pressure in the cylinder or cylinders at any pair of switches having to be
reversed in order to move the said switches the fluid from the main pressure pipe
does not flow direct to the cylinder or cylinders at the switches but is made to enter
one end of a cylinder in or near the signal cabin. This cylinder is one of two
which are placed preferably opposite to each other so that their pistons move a
slotted sliding plate backwards and forwards. Suppose that the pistons act upon the
slotted plate by alternate tension in opposite directions. Then, when the pressure
is admitted to one end of the cylinder in the cabin, which we will call the first
cylinder, the piston is forced forward so as to leave the slotted plate free to move
in the same direction. As the piston is forced forward it drives out the fluid,
already in the cylinder, into the pipe leading towards the cylinder or cylinders
at the switches. The piston or pistons of this latter cylinder or cylinders thus
more and the switches are moved over, if all works properly, the piston having
meanwhile forced the fluid which was already in the cylinder back towards the
signal cabin. This fluid now enters one end of the other (which we will call the
second) cylinder at sigual cabin and forces back the piston which, in it its turn,
forces out the fluid that had been filling the cylinder so that it escapes into the
escape tank to be again pumped at the proper time into the accumulators. The
piston of this second cylinder, also, as it moves backward, pulls back the slotted
plate which had been left free. If the piston of the last mentioned cylinder is able
to move the slotted plate so far as to completely follow up the piston of the first
eylinder it is proof that the switches are working properly; and the slotted plate
releases the handle of the appropriate signal so that such signal can be lowered.
But, if the switches do not work properly, the slotted plate cannot move sufficiently
to release the handle of the signal.
The switch valves being again reversed to put the switches back into their normal
position the converse of the above described operations is effected and the slotted
plate is again forced to the other end of its travel so as to lock the signal or signals

page_text: it had previously released, which will now have risen to danger, and release some
signal previously locked by it.
The arrangement of the valves in connection with this apparatus is similar to
that described and illustrated in my Patent No. 6859 May 3rd 1890 with the
exception that two supplementary valves are now used. The use of these supple
mentary valves is to replace automatically any fluid which may be lost through
leakage or evaporation in the pipes. The supplementary valves may be placed,
one upon each of two short pipes near the cylinders at the signal cabin, connecting
the pipe, leading from the pressure and escape valves to one end of cach cylinder,
with the pipe leading from the other end to the cylinder or cylinders at the
switches. Each supplementary valve will be so constructed that it closes
automatically when the pressure of the fluid on the two sides of it is nearly equal
and that it will in no circumstances permit the passage of fluid flowing back from the
cylinder or cylinders at the switches, and all such fluid is therefore forced to flow
into the cylinders at the signal cabin, but it can be opened by the pressure of the
fluid, if such pressure is greatly unequal in the respective pipes. Thus, if any
leakage or evaporation ocurred, the switches could not be moved fully over by
means of the fluid, but, as soon as the switches had been moved, as far as they
could be, the pressure would be taken off one side of the supplementary valve and
as the pressure would continue to be fully exerted on the other side, the supple-
mentary valve would be opened and enough fluid would pass through it to complete
the movement of the switches. The pressure being then equalised on both sides
of the valve it would close automatically.
It has been assumed in the foregoing description that the object is to move the
slotted sliding plate in the signal cabin by the pulling power alternately of the
pistons of the cylinders at the signal cabin. It might however be preferred to
move the said plate by the pushing power exerted upon it alternately by the said
pistons. The only difference in this case, from the process.described above, will
be that the fluid from the main pressure pipe will, in the first instance, enter one
of the cylinders at the signal cabin at the front end and force the piston back so
as to leave the slotted sliding plate free and drive the fluid already in the cylinder
out at the rear end into the pipe leading to the switches. The fluid returning from
the switches will enter the rear end of the other cylinder at the signal cabin and
force forward the piston to move the slotted sliding plate by its pressure. The
fluid in front of the piston is at the same time forced out at the front end of the
cylinder into the main escape pipe.
The arrangement of the supplementary valves is the same in this case as
previously described.
Though automatically closing valves as above described will probably be
preferable for the supplementary valves it is possible to use valves moved by the
pistons of the cylinders at the signal cabin, which operate the slotted sliding
plates, by the signal handle or by other modifications of the mechanism.
Dated this 20th day of Wahmun 1001
COMPLETE SPECIFICATION.
Improvements in Interlocking the Signals with the Switches on
Railways.
I, CUTHBERT ELLISON CARR, of Hedgeley, Alnwick, in the County of
Northumberland, Engineer, 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 :—
My present invention relates to interlocking the. signal handles with the tongues
of the switches by apparatus alternative to and, in certain cases, preferable to that

page_text: described in my Specifications of Patents Nos. 15,077 dated Sept. 24th 1889, and
6859 dated May 3rd 1890.
In order to ensure that the signalman shall, in every case, know if any pair of
switches has failed to act perfectly, the handles for operating the signals which
are dependent upon such switches are interlocked with the tongues of the switches
by apparatus alternative to the rods and cranks leading from the switches to the
signal cabin, as described and shewn in the before named Specifications, which are
replaced by the fluid itself.
This apparatus consists of two cylinders, preferably placed in or near the signal
cabin, and I will assume that the locking is effected by slotted sliding plates
controlling the passage, through their slots, of notched rods connected with the
signal handles as in my Specification No. 6859.
Each cylinder in the cabin is connected with the cylinder or cylinders at the
switches by a pipe.
The operations are as follows riz.:—
The pressure in the cylinder or cylinders at any pair of switches having to be
reversed in order to move the said switches the fluid from the main pressure pipe
does not flow direct to the cylinder or cylinders at the switches but is made to
enter one end of a cylinder in or near the signal cabin. This cylinder is one of
two which are placed preferably opposite to each other so that their pistons move
a slotted sliding plate which I call the proof plate backwards and forwards.
Suppose that the pistous act upon this slotted plate by alternate tension in
opposite directions. Then, when the pressure is admitted to one end of the
cylinder in the cabin, which I will call the first (or A cylinder), the piston is forced
forward so as to leave the slotted plate free to move in the same direction.
As
the piston is forced forward it drives out the fluid, already in the cylinder, into
the pipe leading towards the cylinder or cylinders at the switches. The piston or
pistons of this latter cylinder or cylinders thus moves (or move) and the switches
are moved over, if all works properly, the piston having meanwhile forced the fluid
which was already in the switch cylinder or cylinders back through the main pipe
towards the signal cabin. This fluid now enters one end of the other (which we
will call the second or B) cylinder in the signal cabin and forces back the piston
which, in its turn, forces out the fluid that had been filling the cylinder so that it
escapes into the escape tank to be again pumped at the proper time into the
accumulators. The piston of this second (or B cylinder) also, as it moves
backward, pulls back the slotted plate which had been left free. If the piston of
the last mentioned cylinder is able to move the slotted plate so far as to completely
follow up the piston of the first cylinder it is proof that the switches are working
properly and the slotted plate releases the handle of the appropriate signal so
that such signal can be lowered. But, if the switches do not work properly, the
slotted plate cannot move sufficiently to release the handle of the signal.
The switch valves being again reversed to put the switches back into their
normal position the converse of the above described operations is effected and the
slotted plate is again forced to the other end of its travel so as to lock the signal
or signals it had previously released, which will now have risen to danger, and
release some signal previously locked by it."
The arrangement of the valves in connection with this apparatus is similar to
that described and illustrated in my Patent No. 6859, May 3rd 1890, with the
exception that two supplementary valves are now used. The use of these supple-
mentary valves is to replace automatically any fluid which may be lost through
leakage or evaporation in the pipes. The supplementary valves may be placed,
one upon each of two short pipes near the cylinders at the signal cabin, connecting
the pipe, leading from the pressure and escape valves to one end of each cylinder,
with the pipe leading from the other end to the cylinder or cylinders at the
switches. Each supplementary valve will be so constructed that it closes
automatically when the pressure of the fluid on the two sides of it is nearly equal
and that it will in no circumstances permit the passage of fluid flowing back from

page_text: the cylinder or cylinders at the switches, and all such fluid is therefore forced to
flow into the cylinders at the signal cabin, but it can be opened by the pressure of
the fluid, if such pressure is greatly unequal in the respective pipes. Thus, if any
leakage or evaporation occurred, the switches could not be moved fully over by
means of the fluid, but, as soon as the switches had been moved, as far as they
could be, the pressure would be taken off one side of the supplementary valve and
as the pressure would continue to be fully exerted on the other side, the supple-
mentary valve would be opened and enough fluid would pass through it to
complete the movement of the switches. The pressure being then equalised on both
sides of the valve it would close automatically.
It has been assumed in the foregoing description that the object is to move the
slotted sliding plate in the signal cabin by the pulling power alternately of the
pistons of the cylinders at the signal cabin. It might however be preferred to move
the said plate by the pushing power exerted upon it alternately by the said pistons.
The only difference in this case, from the process described above, will be that the
fluid from the main pressure pipe will, in the first instance, enter one of the
cylinders at the signal cabin at the front end and force the piston back so as to
leave the slotted sliding plate free and drive the fluid already in the cylinder out
at the rear end into the pipe leading to the switches. The fluid returning from the
switches will enter the rear end of the other cylinder at the signal cabin and
force forward the piston to move the slotted sliding plate by its pressure. The
fluid in front of the piston is at the same time forced out at the front end of the
cylinder into the main escape pipe.
The arrangement of the supplementary valves are the same in this case as
previously described.
Though automatically closing valves as above described will probably be
preferable for the supplementary valves it is possible to use valves moved by the
pistons of the cylinders at the signal cabin, which operate the slotted sliding
plates, by the signal handle or by other modifications of the mechanism.
DESCRIPTION OF DRAWINGS.
The accompanying sheet of drawings shews the application of my invention to a
pair of switches moved in opposite directions by a pair of single acting cylinders
but of course one double acting cylinder will effect the same operations. The
switch cylinders are not in the position they would in an actual apparatus at, or
near to, the switches nor are the other portions of the apparatus in their actual
positions relatively to each other but the drawing shews clearly how the pressure
of the fluid is caused to operate and to replace the rods and cranks leading from
the switches to the signal cabin.
It is assumed to be necessary to prove the accurate working of all "facing"
points, and to be desirable to prove the working of all falling points as well. Plan
shews the apparatus by means of which this can be effected without the use of any
rods, bell cranks, or similar connections, between the switches and the signal cabin,
the return flow of the fluid from the switch cylinders to the signal cabin being
utilised to effect the required proof. The plan shows the apparatus in its
normal position indicating that the switches are also in their normal position and
that the signals for trains passing over the switches in this normal position are free
to be lowered.
Valves 1, 2, 3 & 4 are the valves upon the branch pressure BP and branch
escape pipes BE and which are moved by the signalman when he wishes to move
the switches.
Valves 5 & 6 are supplementary self acting valves, opening one way only, so as
to permit the passage of fluid towards the switch cylinders when, as will be
described below, this may become necessary. Cylinders A, B are supplementary
proof cylinders" placed preferably in or near the signal cabin to work the proof
apparatus. The pistons of these cylinders are connected by a slotted plate SP so
r

page_text: that they can never get further apart than is shewn upon the plan one woma Hot
be prevented from approaching nearer to each other. This connecting slotted
plate SP moves the proof plate" PP immediately below it and this interlocks
with the "proof bars" PB shewn in section which are connected with the signal
handles. Cylinders C & D are the single actiug switch cylinders placed preferably
at or near the switches they move. The pistons of these cylinders are rigidly
fastened together by a connecting bar CB so that they must at all times move
together.
The working of the proof apparatus will now be explained; and, in the first
instance, it will be assumed that the supplementary valves 5 & 6 are not called into
use but remain closed throughout. Assume that the signalman wishes to move the
switches, he reverses the valves 1, 2, 3, 4 by moving the switch handle operating
through the sliding bar SB and intervening levers LL so as to close 2 & 4, and
open 1 & 3.
The fluid under pressure will then flow through valve 3 by pipe l'
into the back of cylinder B and force the piston forward in the direction of the
arrow. The first effect of this is to release the slotted plate SP connecting the
piston of cylinder B with that of cylinder A and to allow the proof plate PP
below, to be moved about half an inch towards the left by means of the
counterweight Wattached to it. This movement of the proof plate PP locks all
the proof bars PB which had previously been free but does not release any of those
previously locked. The two counterweights W & Wattached to the proof plate
are connected with it in two small slots so that both weights can rest on their
supporting blocks when the proof plate is in its central position, and one of the
weights is raised whenever the proof plate is moved from that central position
in either direction. It may be mentioned in passing that the locking of the
proof bars PB occurs in the case of "facing points "just as the wedges or bolt at
the switches begin to move, and long before the switch points are free to move;
and in the case of "falling" points while the switch points are making the first
fractional part of an inch of their motion. As the piston of cylinder B is forced
forward it drives the fluid in front of it out of the cylinder and through the
pipe Pleading to the back end of switch cylinder D. The piston of this cylinder
is then forced forward, in the direction of the arrow, if the switches are working
properly, and forces back the piston of cylinder C in the same direction by the
connecting bar C.B. If however the switches are not working properly the motion
of the pistons of cylinders C & D is arrested. But if they work properly the piston
of cylinder C forces the fluid behind it back through the pipe 12 leading to the fore
end of cylinder A.
As the fluid enters the fore end of this cylinder it forces back the piston in the
direction of the arrow and this drives out the fluid behind it into the pipe 1
leading through the escape valve 1 now open into the storage tank. As the piston
of cylinder A moves back it draws the slotted connecting plate with it, and this
as it approaches the end of its travel moves the proof plate half an inch from its
central position towards the left, thus releasing the proof bars of the signals which
may be lowered when the switches are in their altered position. It is important
to remember that the plate connecting the pistons of cylinders A & B is slotted
and therefore can only be moved by the retiring piston, that is by one whose motion
is caused by the motion of the switches. Also that the movement of the proof
plate PP to release the proof bars PB does not begin in the case of "facing
points until long after the wedges or bolt have passed the points of the switch
rails, and in the case of "falling" points until the switch rails are making the last
fractional part of an inch of their inotion.
::
It is obvious that any failure of the proof apparatus as just described would be a
failure to indicate a full and complete movement of the switches by releasing the
appropriate signal handles, and that failure of the proof apparatus could not result
in indicating a movement of the switches which had not really been completed. It
is nevertheless obvious that a failure of the proof apparatus would cause incon-
venience, and also that the proper working of the apparatus is dependent upon the

page_text: maintenance of a proper supply of fluid in all the pipes and cylinders. It is for
this object that the supplementary self-acting valves 5 & 6 are introduced.
The weights on these valves are not intended to interpose any obstacle to the
flow of fluid through the valves but merely to ensure that they shall close the
moment the pressure of fluid towards the cylinders ceases, and shall not permit any
waste of fluid through them when the pressure is reversed and the fluid begins to
flow back into the front end of the proof cylinders A. & B.
Let it now be assumed that the movement of the switches is to take place with
the supplementary valve 6 open to the pressure of the fluid towards the cylinders
through the pipe P and the supplementary valve 5 closed to the reverse pressure
through the pipe P. As soon as the pressure valve 3 is opened and the escape
valve 4 closed the pressure on the two sides of the piston of cylinder B will be
equal if we ignore the slight balance of pressure due to the absence of a piston
rod at one side. There will therefore be no tendency to move this piston in the
first instance. But the pressure will be fully exerted upon the piston of switch
cylinder D and this and the corresponding piston of cylinder C will move as
before described moving the switches at the same time. The piston of cylinder C
will also drive out the fluid behind it into the pipe P leading to the fore end
of cylinder A and the fluid having no escape from the cylinder through valve 5
which is closed will force back the piston of cylinder A which in its turn will draw
forward the piston of cylinder B to the full extent of its stroke. The piston of
cylinder B will thus travel forward simultaneously with the forward motion of the
piston of cylinder D) and the fluid which flows through the pipe P₁ into the latter
cylinder will as a matter of fact be the fluid forced out of the front end of
cylinder B by the forward motion of its piston, and not fluid passing through the
open supplementary valve 6, provided the pipes and cylinders are full and it is so
far a matter of no importance whether the supplementary valves are open or closed
to the pressure of the fluid moving in the direction of the pistons in cylinders. It.
is when the pipes and cylinders are not perfectly full that the use for these valves
arises. Assume that while the switches were at rest a slight leak or evaporation
has occurred in the pipe leading from cylinder A to cylinder C, this would be
immediately made good by the automatic opening of valve 5, and there would be
fluid enough in the pipes and cylinders to work the proof apparatus efficiently as
soon as the switches were moved. Assume again that the leak or evaporation had
occurred in the pipe leading from cylinder B to cylinder D. It is obvious that
the fluid in the pipe and in the cylinders themselves would not suffice to force the
piston of cylinder D fully out or move the switches or proof apparatus to their full
extent. The deficiency would however be made good through the automatic
opening of the valve 6 as soon as the pressure was admitted to the upper side of it
by the opening of the pressure valve 3 and the closing of the escape valve 4.
Though the proof apparatus as above described and illustrated is designed to be
worked by the backward motion of the pistons of the supplementary or proof
cylinders it might also be made to be worked by the forward motion of these pistons
instead of by their backward motion. In this case the piston rods of the two proof
cylinders A & B would be so arranged that they could not approach each other
nearer than they are when occupying their normal positions but might recede
further apart. The pipes from cylinder A to cylinder C and from cylinder B to
cylinder D would in this case leave cylinders A & C at the back instead of at the
front ends, the pistons acting upon these rods by tension.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what
claim is :-
1st. In apparatus for actuating switches and signals on railways, operated by
fluid pressure a system of interlocking the switch and signal handles to prevent
incompatible or contradictory switches or signals being actuated, or a signal
being lowered until the switches it protects are fully changed and secured;

page_text: alternative to the interlocking systems described in my Patents No. 15077 of 1889
and No. 6859 of 1890 whereby the fluid under pressure is caused, on its return
from the switch cylinders to act upon pistons in cylinders so as to interlock the
switch and signal handles without the intervention of connecting rods from
the switches to the signal cabin substantially as described and illustrated by
the diagram plan.
2nd. In apparatus, such as hereinbefore described and illustrated, the application
of supplementary valves opening automatically to replace loss of fluid by leakage
or evaporation from the accumulator whereby the pipes are always kept full of
fluid and the perfect action of the locking and interlocking of the signal handles
with the switches is ensured and proof conveyed to the signalman of the proper
working of the switches.
3rd. The apparatus for actuating switches and signals interlocking the switch
and signal handles and proving the perfect action of the switches to the signalman
consisting of the pressure and escape valves 1-2 and 3-4 on the branch pressure
and escape pipes BP and BE from the main pressure and escape pipes MP and ME
opened and closed through the slotted bar SB by the switch handles: the
pipes P, and 12 leading to the ends of the proof cylinders A. and B3 and thence
to the switch cylinders C and D: the slotted plate SP, connected with the proof
cylinders A and B, and with the proof plate PP the slots in which control the
movements of the signal handles by the proof bars PB the counterweights W W
to move the proof plate and the supplementary automatic valves 5 and 6 in the
pipes PP and P-P³ the whole combined and operating as described and
indicated by the diagram plan herewith.
Dated this 19th day of November 1901
T. J. DANSON, F. Inst. I. A.,
Chartered Patent Agent, Agent for Applicant.