IMPROVEMENTS IN APPARATUS FOR WORKING RAILWAY SIGNALS
Year: 1876

page_text: LETTERS PATENT to Robert Burn, junior, of Epsom, in the County of Surrey,
for the Invention of "IMPROVEMENTS IN APPARATUS FOR WORKING RAILWAY
SIGNALS."
Sealed the 1st June 1877, and dated the 5th December 1876.
PROVISIONAL SPECIFICATION left by the said Robert Burn at the Office of
the Commissioners of Patents on the 5th December 1870.
ROBERT BURN, junior, of Epsom, in the County of Surrey.
APPARATUS FOR WORKING RAILWAY SIGNALS."
"IMPROVEMENTS IN
My Invention relates to apparatus for working railway signals constructed and
arranged in such a manner as to allow for and compensate variations in the length
of the signal pulls occasioned by changes of temperature, and to secure the correct
working of the signals and their movement to their "danger" attitude in case of
fracture of the pulls.
Signals are usually worked by a hand lever situated in a signal box or cabin,
the said lever being connected by a wire, or wire cord, or other pull, to apparatus
on a signal post (which may be at a considerable distance), whereby the move-
ment is communicated to the semaphore arm and coloured glasses that give the
signals.
Instead of connecting the pull directly to the hand lever I connect it to an arm
or pulley, which is free to move independently of the hand lever, and which is
counterweighted sufficiently to keep the pull always tight, notwithstanding
variations in its length. On this arm or pulley is fixed a toothed circular segment,
and connected to the ordinary spring catch of the hand lever is a tooth or stud,
which can engage with any tooth of the segment.
When the hand lever is at either end of its stroke and held in position by the
spring catch bolt inserted into a notch of the quadrant or circular guides between
which the lever works, then the tooth or stud connected to the spring catch is free
from the toothed segment and the arm or pulley can move so as to allow variations
in the length of the signal pull. But when it is intended to move the signal by
means of the hand lever the spring catch bolt has first to be raised out of the
quadrant notch, and by this movement the tooth or stud connected to it is engaged

page_text: "
with one or other of the teeth of the segment, which then, along with the arm or
pulley to which it is attached, is moved in accord with the hand lever, drawing in
or slacking out the signal pull as the case may be.
When the hand lever has been moved fully over to the end of its stroke its
spring catch bolt is again moved into a notch of the quadrant, and the tooth or
stud connected to it is by this movement disengaged from the toothed segment,
leaving the arm or pulley and the signal pull and counterweight free.
Sometimes a treadle worked by the foot is employed instead of the ordinary
spring catch worked by the hand to release a hand lever at either end of the stroke.
In such cases I connect to the treadle the tooth or stud that engages with the
toothed segment, so that it is engaged when the treadle is depressed preparatory
to moving the hand lever and becomes disengaged when the treadle is released.
When employing this apparatus I prefer to make the counterweight sufficient
not only to take up the slack of the pull but also to overbalance the semaphore arm
of the signal and keep the said signal in its "danger" attitude when it has been
moved to that attitude. If however the pull wire were in such case connected
directly to the semaphore arm, should the pull become broken the signal would
descend by gravity to its "safety" attitude. To provide against accidents from
this cause I introduce on the signal post between the signal pull and the semaphore
arm apparatus which may be variously modified in the forms and proportions of its
parts, but which acts upon certain principles that I will now illustrate by describing
one form in which the parts may be arranged.
The vertical rod which works the semaphore arm is connected to a lever mounted
on the post, and near this lever is a second lever also mounted on the post, and
having on one of its arms a weight sufficient to raise the semaphore arm to its
danger" attitude. On the other arm of this second or loaded lever is mounted a
third or escape lever, one arm of which is connected to the vertical signal rod and
the other to the signal pull, the latter arm bearing against a stop on the loaded
lever. When the signal pull is drawn in, this escape lever is drawn against its
stop, the loaded lever has its weighted arm raised and its other arm lowered, thereby
drawing down the signal rod and raising the semaphore to " danger."
other hand when the signal pull is slacked out the loaded arm of the lever on the
post descends, raising the signal rod and bringing the semaphore down to "safety,"
from which attitude it is moved by drawing in the signal pull, as already described.
If the pull should break, then the escape lever being set free, the loaded arm of the
second lever descends, and after it has descended a certain distance a stud on it
comes to bear against an arm of the first lever, which it moves, thereby raising the
signal to "danger," in which attitude it is retained by the weight on the loaded
lever.
On the
In order to lock the signal at "danger" in its ordinary working I make the
connection to the signal rod by a slotted link allowing a certain play; and I
provide on the loaded lever a catch which engages with a notch on an arm of the
first lever when the signal is at ". danger."
When the pull is slacked for the purpose of lowering the signal the first part of
the movement of the loaded lever serves to remove the catch out of the notch, and
then by its continued movement to raise the signal rod, as already described.
According to a modified form of this apparatus the signal rod is connected to the
arm of a loaded lever by a toggle joint, of which that arm forms one of the
members. The slacking of the signal pull allows this toggle joint to take its
middle position, lowering the signal to safety, but should the signal pull break, the
toggle joint is left free to pass its middle position, and so raise the signal to
danger."
*
Instead of employing a toggle joint for this purpose the signal rod may be made
with a pin working in a curved slot in an arm of the loaded lever, or a pin on this
arm may work in a curved slot in the signal rod, the slot in either case having such
curvature that when the pin is in the middle the semaphore is in the "safety"
attitude, but when the pin is at either extreme of the slot the semaphore stands at
"2

page_text: danger." These points of the slot are preferably notched, so as to hold the pin
steadily in them, unless sufficient force be applied to move it out.
In these modifications an escape lever is employed to bear against a stop when
the toggle is in the middle position or the pin is in the middle of the slot, which
lever when the pull breaks yields, allowing the farther movement to bring the
semaphore to "danger."
A like arrangement of escape lever is applicable to signal apparatus for giving
audible signals, as described in the Specification of a Patent granted to me and
L. J. Green on the 3rd March, 1874, No. 774, and of a Patent granted to me on
the 4th September, 1874, No. 3028.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Burn in the Great Seal Patent Office on the 5th June 1877.
ROBERT BURN, junior, of Epsom, in the County of Surrey. "IMPROVEMENTS IN
APPARATUS FOR WORKING RAILWAY SIGNALS."
My Invention relates to apparatus for working railway signals constructed and
arranged in such a manner as to allow for and compensate variations in the length
of the signal pulls occasioned by changes of temperature and to secure the correct
working of the signals and their movement to their "danger" attitude in case of
fracture of the pulls.
Signals are usually worked by a hand lever situated in a signal box or cabin, the
said lever being connected by a wire, or wire cord, or other pull, to apparatus on a
signal post (which may be at a considerable distance) whereby the movement is
communicated to the semaphore arm and coloured glasses that give the signals.
Instead of connecting the pull direetly to the hand lever I connect it to an arm or
pulley which is free to move independently of the hand lever, and which is counter-
weighted sufficiently to keep the pull always tight notwithstanding variations in its
length. On this arm or pulley is fixed a toothed circular segment, and connected to
the ordinary spring catch of the hand lever is a tooth or stud which can engage with
any tooth of the segment.
When the hand lever is at either end of its stroke and held in position by the
spring catch bolt inserted into a notch of the quadrant or circular guides
between which the levers work then the tooth or stud connected to the spring
catch is free from the toothed segment and the arm or pulley can move so as
to allow variations in the length of the signal pull. But when it is intended
to move the signal by means of the hand lever the spring catch bolt has first
to be raised out of the quadrant notch, and by this movement the tooth or stud
connected to it is engaged with one or other of the teeth of the seginent, which then,
along with the arm or pulley to which it is attached, is moved in accord with the
hand lever, drawing in or slacking out the signal pull as the case may be.
When the hand lever has been moved fully over to the end of its stroke its spring
catch bolt is again moved into a notch of the quadrant and the tooth or stud con-
nected to it is by this movement disengaged from the toothed segment, leaving the
arm or pulley and the signal pull and counterweight free.
Sometimes a treadle worked by the foot is employed instead of the ordinary spring
catch worked by the hand to release a hand lever at either end of the stroke. In
such cases I connect to the treadle the tooth or stud that engages with the toothed
segment, so that it is engaged when the treadle is depressed preparatory to moving
the hand lever, and becomes disengaged when the treadle is released.
When employing this apparatus I prefer to make the counterweight sufficient not
only to take up the slack of the pull but also to overbalance the semaphore arm of
the signal and keep the said signal in its "danger" attitude when it has been
moved to that attitude. If however the pull wire were in such case connected

page_text: directly to the semaphore arın should the pull become broken the signal would
descend by gravity to its "safety" attitude. To provide against accidents from
this cause I introduce on the signal post between the signal pull and the semaphore
arm apparatus which may be variously modified in the forms and proportions of its
parts, but which acts upon certain principles that I will now illustrate by describing
one form in which the parts may be arranged:-
The vertical rod which works the semaphore arm is connected to a lever mounted
on the post, and near this lever is a second lever also mounted on the post and
having on one of its arms a weight sufficient to raise the semaphore arin to its
"danger" attitude. On the other arm of this second or loaded lever is mounted a
third or escape lever, one arm of which is connected to the vertical signal rod and
the other to the signal pull, the latter arm bearing against a stop on the loaded
lever. When the signal pull is drawn in this escape lever is drawn against its stop,
the loaded lever has its weighted arm raised and its other arm lowered, thereby
drawing down the signal rod and raising the semaphore to "danger." On the
other hand, when the signal pull is slacked out the loaded arm of the lever on the
post descends, raising the signal rod and bringing the semaphore down to " safety,"
from which attitude it is moved by drawing in the signal pull as already described.
If the pull should break then the escape lever being set free the loaded arm of the
second lever descends, and after it has descended a certain distance a stud on it
comes to bear against an arm of the first lever which it moves, thereby raising the
signal to
danger," in which attitude it is retained by the weight on the loaded
lever.
In order to lock the signal at " danger" in its ordinary working I make the
connection to the signal rod by a slotted link allowing a certain play, and I provide
on the loaded lever a catch which engages with a notch on an arm of the first lever
when the signal is at "danger."
When the pull is slacked for the purpose of lowering the signal the first part of
the movement of the loaded lever serves to remove the catch out of the notch and
then by its continued movement to raise the signal rod as already described.
According to a modified form of this apparatus the signal rod is connected to the
arm of the loaded lever by a toggle joint of which that arm forms one of the members.
The slacking of the signal pull allows this toggle joint to take its middle position,
lowering the signal to "safety," but should the signal pull break the toggle joint is
left free to pass its middle position and so raise the signal to "danger."
"
Instead of employing a toggle joint for this purpose the signal rod may be made
with a pin working in a curved slot in an arm of the loaded lever; or a pin on this
arm may work in a curved slot in the signal rod, the slot in either case having such
curvature that when the pin is in the middle the semaphore is in the "safety
attitude, but when the pin is at either extreme of the slot the semaphore stands at
"danger." These points of the alot are preferably notched, so as to hold the pin
steadily in them unless sufficient force be applied to move it out.
In these modifications an escape lever is employed to bear against a stop when
the toggle is in the middle position or the pin is in the middle of the slot, which
lever when the pull breaks, yields allowing the farther movement to bring the
semaphore to "danger."
A like arrangement of escape lever is applicable to signal apparatus for giving
audible signals, as described in the Specification of a Patent granted to me and
L. J. Green on the 3rd March, 1874, No. 774, and of a Patent granted to me on
the 4th September, 1874, No. 3028.

page_text: stroke the signal pull is free to undergo variations in its length, but before the hand
lever can be moved the pull becomes rigidly connected to it. A is part of the hand
lever with its spring catch rod B catching in the ordinary way into notches in the
quadrant C at either end of the lever stroke; D is a catch lever mounted on the
main lever A, and connected at one end to the spring catch rod B, the other end
being made to engage with any of the teeth of a toothed segment E which is
mounted freely on the axis of the main lever A. To the segment E is secured a
cross lever F to which is attached the signal pull G, which has a counterweight H
sufficient to put the required stretch upon the pull G. When the lever A is at
either end of its stroke, its spring catch B being then engaged in a notch of the
quadrant C, the catch lever D is disengaged from the teeth of the segment E, and
in that case this segment with the cross lever F is free to move on its fulcrum
according as the pull G becomes extended or contracted in length; but when it is
desired to move the lever A the spring catch B having first to be raised out of the
quadrant notch brings the catch lever D in gear with one or other of the teeth of
the segment E, and then when the lever A is moved the segment E, cross lever F,
and pull G necessarily move with it.
Fig. 2 represents a side view of a locking and escape apparatus according to my
Invention fixed on a signal post for the purpose of working the semaphore signal,
locking it in either attitude and causing it to take the danger attitude in case of the
signal pull being accidentally broken.
Fig. 3 shews the same apparatus in the condition which it assumes when the pull
is broken. The signal pull A is attached to a lever B which is pivotted upon
another lever C and bears with one end against a stop D upon that lever, and with
its other end against a stop E upon a curved lever F which is pivotted at G, and to
which is attached the vertical rod H which works the semaphore signal. The
lever C has on it a counterweight K which is somewhat more than sufficient to
raise the semaphore arm to the danger attitude by acting on a stud L which is fixed
on the lever F. The lever F has at its lower end a slot I in which enters a roller M
pivotted on the end of the lever C. On the pull A being drawn in the lever B is
brought to bear against the stop D, the lever C is moved on its fulcrum raising the
weight K, the roller M depresses the lever F, and thereby draws down the signal
rod H raising the semaphore to the danger attitude. By this movement the roller M
is caused to enter the slot I, and when the stroke is completed it rests in the
recessed part in the end thereof in such a position that notwithstanding great strain
may be applied to the rod H the lever F remains locked, and the signal remains at
danger until by slacking the pull A the weight K is permitted to descend causing
the lever F and rod H to move upwards allowing the signal to descend to its safety
attitude. Should the pull A be broken then the catch lever B being lever free the
weight K descends, and the lever C meeting the stop L causes the lever F to turn
on its fulcrum drawing down the rod H, and so raising the semaphore to its danger
attitude.
Fig. 4 shews a modified form of the apparatus in which an escape lever is provided
to operate in case of the signal pull being broken. In this case a T lever A carrying
the counterweight B has mounted on each of its T arms a pulley C and D (or as
these only operate in case of fracture of the pull they may be merely rounded guide
pins). An escape lever E mounted on the lever A has attached to it the pull F
from the signal lever, and also the pull G extending to the signal post.
It is to be understood that the T arms of the lever A are proportioned to the
respective lengths of the pulls F and G so. as to allow for variations of their length
due to changes of temperature, as described in the Specification of a Patent granted
to me on the 4th Sept., 1874, No. 3028. Should the signal pull F become
broken then the escape lever E being free to turn upon its fulcrum to the position
indicated by the dotted line allows the pull G to run out and the semaphore to be
raised to danger by the counter weight upon the post, notwithstanding the descent
of the lever A, which is limited by any suitable.stop.

page_text: .
A modified form of this apparatus is shewn in Fig. 5, in which case the escape
lever E is dispensed with, and the pull F passes through an eye H upon the lever
A, having on it a ring or stop K which prevents it from being drawn downwards
through the eye H, so that if the pull F should break the remainder of the pull G
is free to run out.
Fig. 6 is a side view of apparatus on the signal post for working the semaphore by
means of a toggle joint. In this case the counterweighted lever A, to which is
attached the signal pull B, has an arm C forming one member of a toggle joint, the
other member of which is a link D connected to a lever E which works the vertical
signal rod F.
A counterweighted locking lever G is made with a catch to engage
with the end of the lever E, as shewn, the tail of the lever G resting on the pin at
the end of the arm C which works in a slotted hole in the link D. When the pull
B is drawn in so as to raise the weight of A and to bend the toggle joint the lever E
and signal rod F are pulled downwards; raising the semaphore to danger, the catch
lever G thereupon engaging with the end of E and so locking the signal at danger.
On slacking the pull B the loaded end of the lever A descends, its arm C throws off
the catch G, and the straightening of the toggle joint raises the lever E and signal
rod F, thereby lowering the semaphore to its safety attitude. Should the pull B
break then the weight on the lever A causing the toggle to pass its middle position
so as to become bent in the opposite direction draws down the lever E and rod F,
thereby raising the semaphore to danger.
Fig. 7 represents a modified apparatus, in which a roller or stud upon a loaded
lever working against the curved face of a signal lever is substituted for the toggle
joint arrangement last described. Here the loaded lever A, to which is attached
the pull B, has a stud or roller C bearing against the curved face of the bell crank
lever D, to which is connected the signal rod E. The curved face of D is recessed
at its middle and its two extremes so as to give rests for the stud or roller C.
When the pull B is drawn in the weighted arm of A is raisd and the stud or roller
C acting on the face of D causes that lever to turn on its fulcrum pulling down the
rod E, and thereby raising the semaphore to danger, in which attitude it is kept
with considerable firmness by the stud or roller C resting in the upper recess of D;
on slacking the pull B the loaded arm A descending to the position shewn in Fig. 7
causes the semaphore to be lowered. Should the pull B break the loaded arm A
descending further raises the semaphore to danger. Fig. 8 represents a similar
apparatus in which the stud or roller is mounted in the bell crank lever of the signal
and the curved face is provided on the loaded lever.
The arrangement which I have above described for working. semaphores upon
signal posts are obviously applicable, with suitable modification, for working signals
of other descriptions, such as discs.
Having thus described the nature of my Invention, and in what manner the
same is to be performed, I claim,―
First. Disconnecting the hand lever for working a signal from the pull of that
signal except during the stroke of the hand lever, substantially as and for the pur-
poses set forth with reference to Fig. 1 of the accompanying Drawings.
Second. Connecting a signal pull to the loaded lever which works the signal by
ineans of an escape lever or its equivalent, so arranged that when the signal pull
breaks the signal is moved to its danger attitude, substantially as herein described
with reference to Figs. 2, 3, 4, and 5 of the accompanying Drawings.
Third. Connecting the loaded lever which works a signal to the signal rod by
means of a toggle joint so arranged that when the signal pull breaks the said toggle
by passing its middle position causes the signal to be moved to danger, substantially
as herein described with reference to Fig. 6 of the accompanying Drawings.
Fourth. The use instead of toggle joint referred to in the preceding claim of a
stud or roller working against the curved face of a lever, substantially as herein
described with reference to Figs. 7 and 8 of the accompanying Drawings.
Fifth. The method of locking a signal in the position to which it has been

page_text: moved, substantially as herein described in Figs. 2 and 3 of the accompanying
Drawings.
In witness whereof, I, the said Robert Burn, junior, have hereunto set my
hand and seal, this Fifth day of June, in the year of our Lord One thousand
eight hundred and seventy-seven.
ROBERT BURN, JUN. (L.S.)