Pneu-mat′ic tube.
To the fertile brain of
Dr. Papin of
Blois, who lived about the end of the seventeenth century, we are indebted for the first suggestion of conveying parcels in a tube by means of compressed air. This distinguished Frenchman was the first to adopt a piston in the cylinder of a steam-engine.
He invented the digester, which is the progenitor of a host of lard-tanks and rendering devices.
He was the inventor of the weighted-beam safety-valve.
He was the first, so far as we know,
[
1756]
to suggest the use of compressed air conveyed by pipes as a means of transmitting power.
See page 26.
After the death of the doctor, the invention took a sleep for a century, which might be a long sleep for anything else, but is for an invention only a reasonable nap. Sixteen or seventeen centuries elapsed between the double-cylinder fire-engine of Ctesibus of
Alexandria and the similar engine of
Nuremberg.
The aeolipile of Hero is substantially analogous to the water-wheel of the worthy
Dr. Barker, who left us a century back or thereabout, except that the fluid agent of one is
steam and of the other
water. The principle is the same, and the turbine invented by Fourneyron, in 1823, does not differ in its principle of action from the aeolipile of Hero, 150 B. C., or the reaction water-wheel of
Barker, say A. D. 1740.
We are much indebted to the worthy
Otto Guericke, a magistrate of
Magdeburg, for re-inventing the air-pump, about 1650; but Hero, 1,800 years before, had used an air-pump to condense air in a chamber above water to make an artificial fountain.
The splendid French edition of
Hero's “Spiritalia” was published in
Paris during the reign of
Louis XIV., — not so very long after the good burgher of
Magdeburg had set the ball rolling again.
What
Archimedes did for the fleet of
Marcellus at
Syracuse, 212 B. C.,
Proclus did for the ships of Vitalian at
Constantinople some 700 years afterward, and
Buffon performs the same feats with burning mirrors in a peaceable way, about the middle of the last century, upon metals, green wood, and various intractable minerals.
See page 410.
In 1810, Medhurst took out a patent in
England for a means of conveying goods, letters, parcels, and passengers by means of a tube and a blast of compressed air. (
Plenum.) He proposed to apply it to driving passenger-cars at the rate of fifty miles per hour, the cars taking the shape of the tube.
In 1824, Vallence received an English patent for a substantially similar mode, excepting that the air was exhausted in front of the carriage, and the latter was driven by atmospheric pressure. (
Vacuum.)
In 1835, Pinkus, an American in
England, changed the scheme, the motion of a piston in the tube being transferred to a carriage traveling outside.
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Beach's pneumatic dispatch. |
This takes it out of the domain of our subject, in which the tube is the means of transmission.
The subject of farther improvements in the line of the invention of Pinkus is pursued under atmospheric Railway.
The pneumatic dispatch-tube was started by a company in
London in 1859, for conveying parcels and light goods between the
Euston Square Station and the Post-Office in Eversholt Street,
London.
A continuation to Holborn was opened in 1865.
The pneumatic tube for the transmission of passengers or goods has been brought into prominence in the
United States by the exertions of
A. E. Beach of New York, and passengers were conveyed in an experimental section of tube at the Cooper Institute Exhibition, 1867.
Mr. Beach has patented many special appliances having reference to the working of pneumatic tubes, and among the rest one for delivering letters, parcels, etc., November 13, 1866.
The pneumatic tube is traversed by a car, which receives and delivers letters at intermediate stations and at the ends of its route.
Devices actuated by the car in passing, or controlled by an electromag-netic apparatus from an office, arrest the car either for the reception of letters from a receiver or their deposition at a given point, as the devices may be arranged or actuated by the electro-magnetic connection.
A passenger and freight railway on
Beach's plan has been constructed for some distance under
Broadway, New York, the intention being to extend it from the
Battery to
Harlem.
For a number of years past the telegraph-offices of
London have communicated with the central office by pneumatic tubes, in which the air is exhausted in front of the carrier and condensed behind it: these tubes are arranged in circuits, so that the current of air is continuous and conveys parcels in each direction at the same time.
At each way-station on the line is a receiving apparatus consisting of two short barrels parallel with the main tube, either of which may be put in or out of connection with the line: one of these is open at both ends, so that a carrier may pass through unimpeded, but the other is closed at one end, with the exception of a small opening, so that when it is switched into line with the main tube it intercepts the carrier.
The time when a carrier may be expected to arrive is telegraphed to the receiving station.
In the telegraph pneumatic dispatch at
Liverpool the messages are placed in little round bags, accurately fitting the tube, and urged forward by compressed air under a pressure of eleven pounds to the square inch.
The tubes are connected, one with a vacuum chamber and the other with a compressed air-chamber; air being compressed in one and exhausted in the other at the same time by a double-barreled air-pump, operated by an engine working at about one horse-power. A speed of about forty miles an hour is attained.
Within the past few years the pneumatic tube has been applied to some extent for the transportation of passengers and freight as well as letters and parcels.
Such is that between Holborn and Euston Square in
London.
In this the tube at the straight portions consists of iron pipes, cast in 9 feet lengths, 4 feet wide, and 4 feet 6 inches high.
The curves vary from 70 to 300 feet radius, and the gradiants from 1 in 60 to 1 in 40, some portions of the line being level.
The trucks run on rails laid on longitudinal sleepers, and are about 10 feet long; they have an elastic binding at their ends, allowing a small interval between this and the sides of the tube to avoid friction, a perfect vacuum not being required: they weigh 1/2 ton, and carry a load of 1 1/2 tons; in ordinary working, 24 trains, a gross weight of 240 tons, have been carried over the road in four hours. The air may be either forced or exhausted, the pressure required usually not exceeding 1/2 pound per square inch.
These operations are effected by a fan 22 feet in diameter, driven by an engine having a pair of 24-inch cylinders of 20-inch stroke.
Brisbane's carrier, for pneumatic tubes, is made of spherical or cylindrical shape, so as to rotate when set in motion, avoiding the friction due to the pressure of the weight on bearings.
[
1757]
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Pneumatic tube. |
