IMPROVEMENTS IN RAILWAY SIGNALS FOR ENABLING PASSENGERS TO COM- MUNICATE WITH THE GUARD AND ENGINE DRIVER OF RAILWAY TRAINS
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by David Alfred Aird at the Office
of the Commissioners of Patent, with his Petition, on the 12th
August 1875.
I, DAVID ALFRED AIRD, of Figtree Court, Temple, in the City of
London, Barrister, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN RAILWAY SIGNALS FOR ENABLING PASSENGERS TO COM-
MUNICATE WITH THE GUARD AND ENGINE DRIVER OF RAILWAY TRAINS," to be as
follows:-
The object of this Invention is to enable any passenger in a train to
produce an audible signal which will attract the attention of the guard
and engine driver, so that the train may be stopped should anything be
amiss. Various attempts have been made from time to time to effect
this object, but they have all so far as I am aware necessitated the use
of cords, wires, rods, tubes, or equivalent devices, for the purpose of
effecting a continuous communication from end to end of the train.
This has been found to be very inconvenient in making up or dividing
trains, and is open to many objections not the least of which is the
difficulty and uncertainty of working the signal when the train is
composed of many carriages. To avoid these and other objections I
provide cach carriage with a distinct and separate signalling apparatus
which will not require to be connected with the adjoining or contiguous

page_text: carriages, so that in making up a train the railway servants will not
have to look after any but the ordinary couplings for connecting the
carriages.
My improved audible signal consists of an explosive compound, gun-
powder by preference, which is placed in a short barrel like part of a
gun barrel, and so arranged that the charge can be exploded by means
of a percussion cap or other detonating device. The most convenient
way of carrying out my Invention is to enclose the explosive substance
in a cartridge, which if desired may contain its own fulminate as in the
metallic cartridges usually employed in breech-loading rifles. Or the
cartridge may be exploded by means of a percussion cap placed on a
nipple screwed into the breech of the barrel. The cap or fulminate in
the cartridge is exploded by a blow from a firing pin or hammer, which
when released from the trigger or other equivalent device (which holds
it back in the firing position) is driven forward by a coiled or other
spring. The barrel may be placed either horizontally, vertically, or in
an inclined position, and the whole apparatus is enclosed in a box which
is placed outside on the roof of the carriage, an aperture being made in
the casing for the exit of the flame and gases produced by the explosion
of the charge. The trigger or other equivalent device is worked by
means of a cord, wire, or chain, the end of which is passed through a
hole in the roof, and is provided with a ring or handle whereby it may
be pulled when required to discharge the signal. Each compartment of
the carriage may be provided with one, two, or more cords com-
municating with the trigger, so that every individual passenger may
have a convenient means of producing the signal.
The gun barrel may be hinged to the framing of the apparatus or be
easily detachable therefrom if desired for the convenience of charging the
same, and the open mouth of the barrel may if desired be closed by a
soft light plug for the purpose of keeping out wet.
In order to indicate to the guard or driver the particular carriage and
compartment from which the signal has been made, the signal cord is
made to raise or throw out a disc or visible signal on each side of the
carriage.