IMPROVE- MENTS IN RAILWAY SIGNALLING APPARATUS
Year: 1875

page_text: LETTERS PATENT to David Alfred Aird, of Fig Tree Court, Temple,
in the City of London, Esquire, for the Invention of "IMPROVE-
MENTS IN RAILWAY SIGNALLING APPARATUS."
.
PROVISIONAL SPECIFICATION left by the said David Alfred Aird
at the Office of the Commissioners of Patents, with his Petition,
on the 21st October 1875.
c
I, DAVID ALFRED AIRD, of Fig Tree Court, Temple, in the City of
London, Esquire, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN RAILWAY SIGNALLING APPARATUS," to be as
follows:-
The Invention has for its object improvements in railway signalling
apparatus, and relates to the employment of means or apparatus, whereby
when the ordinary semaphore signal arm is placed at "danger" a
detonating signal is also placed in position to be exploded by a hammer
or striker acted upon by the wheels of a train. For this purpose I place

page_text: any convenient or necessary number of detonating or audible signals
(which may be of a similar character to ordinary "fog signals," but
without the clips) in a tube or reservoir one above another. At the
bottom of this tube in suitable guides is fitted a slide, which when in
one position is capable of receiving one of the detonating signals, and
then when slidden outwards carries such detonating signal into position
to be acted upon by a hammer or striker which is attached to or acted
upon by a spring or lever mounted on one side of a rail in position to be
depressed by the flanges of the wheels passing over it.
"
The slide is by suitable attachments connected to the means or
apparatus acting upon the semaphore, so as to cause the semaphore and
slide to be simultaneously operated. By theso means when the signal
arm is placed at "danger the slide is simultaneously caused to move
forward and carry with it a detonating signal into position to be struck
by the hammer or striker, and then when the signal arm is placed at
"all clear" the slide is moved in the contrary direction and carries back
with it the detonating signal, if such has not been exploded, ready to bo
again placed in position when required, whilst if the detonating signal
has been exploded it will, consequent on its having been crushed and
spread out by the blow it has received, be pushed off the slide by the
sides of the guide, thereby leaving the slide again ready to receive a
detonating signal from the reservoir.
This arrangement of apparatus is also applicable to what is known as
the "block system" of signalling. For this purpose I arrange a
signalling apparatus as above described at each signalling station, but I
also connect each signalling apparatus by electrical or other attachments
to the signalling apparatus at the station next to the rear thereof, by
which means when a signal is set to "danger" at one station the
attachments therefrom will act upon the signalling apparatus at the
station next to the rear thereof, and cause the slide to carry the
detonating or audible signal out of position to be acted upon by
the hammer or striker, and at the same time place the signal arm to
"all clear." In this arrangement the signals may be operated by hand
or by self-acting means of any of the well known descriptions.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David Alfred Aird in the Great Seal Patent
Office on the 21st April 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
ALFRED AIRD, of Fig Tree Court, Temple, in the City of London,
Esquire, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-first day of October, in the
year of our Lord One thousand eight hundred and seventy-five, in
the thirty-ninth year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said David Alfred Aird,
Her special licence that I, the said David Alfred Aird, my exc-
cutors, administrators, and assigns, or such others as I, the said
David Alfred Aird, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United King-
dom of Great Britain and Ireland, the Channel Islands, and Isle of
Man, an Invention for "IMPROVEMENTS IN RAILWAY SIGNALLING Apparatus,"
upon the condition (amongst others) that I, the said David Alfred
Aird, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed
in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said David Alfred Aird, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say :—
The Invention has for its object improvements in railway signalling
apparatus, and relates to the employment of means or apparatus, whereby
when it is desired to indicate "danger" a detonating signal is placed in
position to be exploded by a hammer or striker acted upon by the wheels
of a train. For this purpose I place any convenient or necessary number

page_text: reservoir a when such recess c¹ is immediately under such tube or
reservoir. The slide has attached to the ends thereof wires or
chains c, c, by which it is operated. The chain or wire c is connected
to suitable apparatus by which the slide may be drawn in that direction,
as will be readily understood, and the chain or wire passes over a
guide wheel, and has connected thereto a weight (or it may be connected
to a spring) by which the slide when released by the signalman is drawn
into the position shown in Figure 2, with a sigual in position to be
exploded by the hammer or striker d on the passing of a train over the
lever e.
This lever is mounted on an axis of motion at e, and is
provided with a counterbalance weight to return it to its normal
position after having been depressed by the wheels of a train.
in
Instead however of employing a lever e a spring of a somewhat similar
form may be placed in a similar position to effect the same purpose.
Thus when the slide c is drawn by means of the chain or wire c³, so as
to place the recess c² immediately under the tube or reservoir a a signal
b falls into such recess c¹; then when the slide c is drawn by means of
the chain or wire into the position shown in Figure 2, the signal
the recess c¹ is in position to be exploded by the wheels of a passing
train acting upon the lever or spring e and hammer or striker d. If
however it is desired to indicate "all clear," the slide is drawn back by
the wire c³, when if the detonating signal & in the recess c' has not becn
exploded it will remain in the recess c³ in readiness to be again placed
in position to indicate "danger," whilst if the detonating signal has
been exploded it will, consequent on its having been crushed and spread.
out by the blow it has received, be pushed off the slide by the sides of
the guide, thereby leaving the recess in the slide b again ready to receive a
detonating signal from the tube or reservoir a. The sides of the guides
for the slide c are inclined, as shown to enable them the more readily to
throw off an exploded signal, but if desired the end flange c of the
slide c may be hinged to the slide c and retained in its normal position
by a spring or weight, so that in the event of any resistance being
offered to the motion of the slide c by the exploded signal, such end
flange c¹ would give way and permit the exploded signal to be pushed
over it off the slide c.
Instead of operating the slide c in the one direction by the chain c³
and a weight, it may as will be well understood be operated in that
direction by a lever acted upon by a weight or spring.

page_text: My improved arrangement of apparatus may be employed as an
independent apparatus, or it may be connected to and be operated
simultaneously with the ordinary semaphore signalling apparatus.
If it is required to employ a greater reserve of detonating or audible
signals than can be conveniently placed in a single tube or reservoir a,
two or more of such tubes or reservoirs may be placed side by side, and
a greater extent of motion may be given to the slide c, so as to cause the
recess c¹ to pass under all of the tubes or reservoirs c at each action
thereof, such slide being suitably lengthened at the end o* thereof to
enable it to retain the signals b in the tubes or reservoirs a, except as
they are delivered one by one to the recess c¹ in the slide c.
I have not thought it necessary to give a Drawing of this modifi-
cation, as such will be readily understood by a competent mechanic.
This arrangement of apparatus is also applicable to what is known as
the block system" of signalling.
" of signalling. For this purpose a signalling
apparatus is arranged as above described at each signalling station, but
cach signalling apparatus is also connected by electrical or other attach-
ments to the signalling apparatus at the station next to the rear thereof,
by which means when a signal is set to "danger" at one station the
attachments therefrom will act upon the signalling apparatus at the
station next to the rear thereof and cause the slide c to carry the
detonating or audible signal out of position to be acted upon by
the hammer or striker, and at the same time place the signal arm to
"all clear." In this arrangement the signals may be operated by hand
or by self-acting means of any of the well known descriptions.
I would here remark that since filing my Provisional Specification I
have been informed that it has before been proposed to connect
semaphore signalling apparatus with fog or audible signalling apparatus;
I do not therefore claim such combination.
Having thus described the nature of my said Invention and the mode
in which I propose to carry the same into effect, I would have it
understood that what I claim is the peculiar arrangement and com-
bination of signalling apparatus, substantially as herein shown and
described, whether used separately or in combination with semaphore
signals by which a detonating or audible signal may be taken from a
reservoir by a slide, and carried into position to be struck by a hammer

page_text: or striker acted upon by the wheels of a passing train, engine, or vehicle,
in lieu of their being placed in position by hand or by mechanical means
on the rail to be exploded by the direct action thereon of the wheels of
a passing train, engine, or vehicle as heretofore.
In witness whercof, I, the said David Alfred Aird, have here-
unto set my hand and seal, this Twenty-first day of April, in
the year of our Lord One thousand eight hundred and seventy-
six.