IMPROVEMENTS IN ATMOSPHERIC RAILWAYS
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by Alexander Alison and James
Halliwell at the Office of the Commissioners of Patents, with their
Petition, on the 18th December 1863.
We, ALEXANDER ALISON, of No. 72, Sloane Street, Chelsea, in the County
of Middlesex, Gentleman, and JAMES HALLIWELL, of No. 2, Queen Street
Place, in the City of London, Railway Contractor, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN ATMOSPHERIC RAILWAYS,"
to be as follows:-
These improvements relate chiefly to the novel construction and arrange-
ment of the valve on the air tube, and mode of operating the same; to
the use of a double piston, and to the means employed for stopping the train
at the stations, or any other points on the line. The valve extending the
whole length of the tube is composed of short, bent, or trough-shaped plates
or links, and for this reason is designated a "chain valve." These plates may
be secured together by means of a band or sole of leather, or other suitable
material, which band will effectually prevent the passage of air from or into
the tube. The ends of the plates which form socket or hinged joints may be
fastened together by means of pins if found desirable. The plates or links
forming the valve are constructed with longitudinal trough-shaped openings
upon their upper surface. A continuous flexible valve similar in shape to the
"chain valve" may be substituted for the latter. Both the flexible and the
"chain valve" are moved off the aperture in the air tube to admit the passage of
the pistou rod, and afterwards returned to their original position by a horizontal

page_text: curved bar so fixed on the piston rod that it passes through the longitudinal
trough-shaped opening in the upper side of the said valves. As the piston
rod travels the front part of this curved bar, which is in advance of the piston
rod, removes the successive links or portions of the flexible valve, and the rear
part returns these to their former position in whichever direction the train is
moving. The valve is placed in a chamber made on the air tube. This
chamber, which has an opening to admit the passage of the piston rod, is so con-
structed that the valve is freely moved horizontally by the action of the curved
bar. The top of the chamber, which is constructed to fit closely upon the
valve, is adjustable for the purpose of tightening the said valve, thereby pre-
venting the passage of air from or into the tube. All or a portion of the
plates may be provided with a guiding pin to prevent the "chain valve " from
moving longitudinally. A double-headed piston is employed for the purpose
of securing steadiness in the same when passing through the tube, also to
enable the train to be more readily stopped at any desired point, and to admit
air into the tube between the two heads of the piston before and behind the
piston rod as the piston travels, the heads of the piston being about twelve
feet from each other. While running the train, one or both of the heads
of the piston may be closed as circumstances render desirable. There
may be valves formed in the piston heads, or the latter may be con-
structed to act as valves as found most convenient and efficient.
Valves are
fixed in the tube at suitable distances along the line for the purpose of
destroying the vacuum in front of the piston, and creating a partial vacuum in
the rear, in which case both heads of the piston should be closed. The valves
as well as the piston heads are opened and shut at the pleasure of the con-
ductor by any suitable device. A valve located in front, and another in the
rear of the train is closed by the conductor when it is desired to stop the
carriages. In this manner not only is the vacuum destroyed immediately in
the front of the train, but by opening the forward head of the piston to admit
the air, and afterwards closing the same as the train approaches, the closed
valve in front forms an air cushion in the tube, thereby gently stopping the
train; but to avoid excessive pressure in front, the tube is provided with safety
valves at suitable distances to permit the escape of the compressed air.
To prevent the oscillations of the piston carriage or train being communicated
to the piston, a hinged joint is supplied to the piston rod. The size of the air
tube may be advantageously constructed considerably larger than those usually
employed for atmospheric railways, by which construction sufficient power to
drive the train may be obtained by a lower pressure, thereby lessening the
necessity of having the piston working in the tube perfectly air-tight.

page_text: Two stationary engines which work jointly or separately are employed at
each section, and at either end of the railway. These engines working pumps
or fans should be of a size sufficient to give the required power, and by our
construction of the piston, the power may be increased by forcing the air in
the rear, as well as by creating the vacuum in the front of the piston. By
this means, the power may be doubled or quadrupled with a close fitting
piston.
This improved atmospheric system of railway has special advantages over
the locomotive railway for ascending and descending heavy gradients, also
enabling the cost of construction to be greatly reduced, while the expense of
the plant, the wear and tear of the same, and the repairs of the permanent
way, are much less than on a locomotive line.