IMPROVEMENTS IN THE MEANS AND APPARATUS EMPLOYED FOR CONVEYING TELEGRAPHIC DISPATCHES, LETTERS, AND OTHER LIGHT ARTICLES THROUGH TUBES
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Charles William Siemens at the
Office of the Commissioners of Patents, with his Petition; on the 24th
November 1866.-Partly a communication from abroad by Dr. Werner
Siemens, of Berlin, in the Kingdom of Prussia.
I, CHARLES WILLIAM SIEMENS, of No. 3, Great George Street, Westminster,
in the County of Middlesex, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE MEANS AND APPARATUS EMPLOYED FOR CONVEYING
TELEGRAPHIC DISPATCHES, LETTERS, AND OTHER LIGHT ARTICLES THROUGH TUBES,"
to be as follows:-
In the arrangements heretofore employed for conveying letters or parcel's
through pneumatic tubes from one station to another the one end of the tube
has been made to communicate with the one station, and the other end has
been made to communicate with the other station, and the letters or parcels
have been conveyed through the tube inside pistons or cylindrical carriages
caused to travel along the tube either by exhausting the air from the tube in
front of the piston or by forcing air into the tube behind the piston, or by both
methods combined.
By the present Invention pneumatic tubes are so arranged as to have no
terminal points, but to form closed pneumatic circuits communicating at one
point (a central station) with an air pump which causes the air to travel
round and round in the tube continually in the same direction, so that on
introducing a piston or cylindrical carriage containing the dispatches into the
tube at such pumping station it would, if not intercepted at an intermediate

page_text: :
'point, be caused to travel right round the circuit, and thus eventually arrive
at the pumping station again. At intermediate points in the pneumatic
circuit thus established are situated the stations to or from which dispatches
are to be conveyed from or to the central or pumping station. For conveying
dispatches from these intermediate stations to the central station, or vice versa,
they are made to communicate with the circuit by means of a branch pipe
into the one end of which the piston is introduced, and whence, after closing
the said end thereof and then establishing a communication at the other end
with the circuit, the piston is made to pass into the circuit, where it is pro-
pelled by the circulating air so as to arrive at the central station. For
receiving dispatches or parcels from the circuit into the stations a portion of
the tube forming the circuit is arranged similar to a "switch" on railways,
that is, at one point it is capable of being moved away from the circuit and
made to communicate with a closed chamber into which the piston or cylin-
drical carriage containing the dispatches destined for the particular station is
consequently caused to pass from the circuit, its momentum being gradually
absorbed in such chamber by a series of brushes arranged longitudinally, so
as, to produce a powerful drag upon the piston; or such retardation may be
effected by causing the piston to compress the air in front of it in the chamber,
in the end of which a small hole is made so as to allow the compressed air to
escape in order to prevent rebound; this chamber is closed at the sides and
end, and is provided with a door opening on hinges for removing the dis-
patches or parcels therefrom. While the circuit or main tube is thus directed
into the receiving apparatus the circulation of air in the same nevertheless
continues through a by-pass branching from the main tube at each inter-
mediate station immediately in front of and behind the moveable or "switch"
point. The before-mentioned branch for dispatching the parcels from the
stations is, by preference, so arranged that when the main tube is diverted at
one point, into the receiving chamber, thus leaving an opening in the main
tube at that point, such dispatching branch is simultaneously moved in front
of the opening in the main tube, whereupon owing to the branch being placed
in an inclined position the piston or cylindrical carriage that has previously
been placed in such branch passes down into the main tube by gravity and is
then urged forward by the circulating current of air. When the pueumatic
circuit is of considerable extent and the tube is of small diameter the speed of
transit of the pistons may be considerably increased by the employment of
hydrogen or light carburetted hydrogen gas in the tube in place of atmospheric
air, which gas might be supplied continually at the pumping station to make
up for losses through leakage, and to prevent such leakage the maximum

page_text: [pressure in the tube may be made never to exceed that of the external
atmosphere, which may also be preferable even when atmospheric air is used.
In introducing fresh air or gases into the tube to make up for leakage such
air or gases are, by preference, first made to pass through a drying chamber
containing dry lime or other substances that will take up the moisture from
the air or gas before it enters the tube.
As a number of the pistons or cylindrical carriages may require to be
continually dispatched from the central station to the several intermediate
stations on the circuit information is conveyed to the particular station for,
which a certain carriage is destined by means either of an electric telegraph
signal which is given at the central station at the time when the carriage is
introduced, and by causing the said signal to set in motion a clockwork
mechanism at the said station a second signal may thereby be given after a
lapse of time corresponding with the time the carriage takes to travel from
the central station to the intermediate station in question, thereby warning
the attendant of the proper moment when he has to divert the main pipe into
the receiving chamber; or the carriages may be dispatched at preconcerted
intervals of time to the respective stations, where electric clocks are made to
indicate to the attendants the exact time when they have to expect a carriage;
or the attendant at any one intermediate station may be guided as to the
precise moment when to move the tube for the reception of a message by
means of the vibration produced in the tube itself by the approaching carriage.
In order to render these vibrations sensible at the station the tube may be
laid hollow upon supports for a certain distance before the station, and a
signal may be received either by the transmission of sound through the tube
only or by means of a pendulum, ball so suspended as to touch the tube, with
a contact point opposite through which a galvanic circuit, including an alarum,
can be brought into action the moment the vibratory motion of the tube
causes the pendulum to rebound upon the contact point. A number of the
before-described pneumatic circuits may be made to communicate with one
central station, and in large towns one or more of the intermediate stations on
any circuit may be constituted a branch central station, from which again a
series of pneumatic circuits may branch out. At stations where carriages
come in at very frequent intervals two or more receiving chambers may be
provided, into which successive pistons may be "switched" in rotation to
allow time for their removal. The carriages employed for transmitting the
dispatches or parcels are, by preference, made cylindrical in form, and are so
arranged that they can be opened for the introduction of dispatches, letters,
or parcels, and they are provided in front and behind with a pair of wheels at

page_text: right angles to each other, each wheel being nearly of the internal diameter
of the tube itself. The body of the cylinder or piston need not touch the
internal surface of the tube because the friction produced by the wheels is so
slight as to render a close fit not necessary.
It will be readily understood that in working pneumatic circuits on the
above-described principle a great number of pistons may be travelling within
the tube at the same time, both coming to and going from the central and
intermediate stations, thus rendering this system capable of forwarding a
great number of dispatches or parcels at frequent intervals without its being
for this purpose necessary to attain a high rate of speed of transit.