The San Francisco call., 1904-03-20
INSTRUCTIVE JTUDEnS
By YhNOIEAAEEE,N AND
%ASTfEN

and provided with a hinged lid, which
can be quickly and securely locked at
the other end. For an eight-inch tube
the carrier is two feet long and seven
inches in diameter, and weighs empty
about thirteen pounds. The steel shell
Of the carrier never touches the pneu-
matte tube. for on each carrier are two
collars made of woven cotton cloth.
tightly clamped between metal rings
These collars when new fit the pneu-
matte tube snugly, but use wears them
down until sometimes they are a quar-
ter Of an inch smaller than the dame
ter of the tube. One would think that
this would permit so much air to es-
cape past the collars that the carrier
would lose speed, but as a matter of
fact this affects their velocity but
slightly. The collars are good for about
2O00 miles of travel. Then they are re-
newed. The empty carrier weighs
about thirteen pounds, and its carrying
capacity is somewhat over 800 cubic
inches. Apparently ii makes no differ
ence so far as speed in transit is con-
cerned whether the carrier is empty or
full. The builders Of pneumatic tube
systems claim that a carrier filled with
brick or lead will shoot through the
tube, as swiftly and certainly as one
filled with feathers.
The company which installed the
pneumatic transmission service in Phil
adelphia had in mind the expansion Of
the service to- adapt it to commercial
uses. In order to determine the best
size of tube for carrying miscellaneous
bundles and packages of retailed mer-
chandise a series of tests were made.
The ingenious method of measuring
bundles by passing them through hoops
Of iron was adopted. Men were sta
toned in several large department
stores where all packages and bundles
for delivery were carried out. Every
bundle was put through rings and 1t
was ascertained that 81 per cent Of all
packages and bundles could be packed
in a 12-inch carrier, about 10 per cent
less could go in a 1O-inch carrier and
90 per cent in an S-inch carrier. 1t was
demonstrated that large proportion
of the bundles too large to be sent
through a Pinch tube could be re-
wrapped so as to permit their passage
through an S-inch tube.
At each station of a pneumatic tube
line. whether a terminal or an inter-
mediate station, is an apparatus for
sending and receiving carriers. The de-
vice is SO arranged and managed that
there is no break in the current of air
while the carrier is being pushed into
the main tube. A frame carries two
sections of tubing. When at rest one
section forms part of the main tube.
The carrier is thrust into the open tube,
an air motor governed by a starting
lever swings the frame until the sec
ton containing the carrier comes to po-
sition, forming part of the main tube;
the air Immediately drives the carrier
into the main tube and swiftly trans
ports il to the other terminal. When
the carrier arrives at station it
shoots into closed receiver, and, COM
pressing the air, forms an air cushion
so that il comes to rest without
shock This closed receiver then tips
down, discharging the carrier, and then
automatically returns to its original
position ready to catch the following
receiver.
Carriers can be sent to intermediate
stations, where an ingenius device au-
tomatically switches from the main
line only such receivers as are destined
for that station. A small metal disk on
one end of a carrier determines whether
the carrier will be switched aside from
the main line. In the bottom of the re-
ceiving tube, at the intermediate sta
I4-1-
wide enough to span the space be-
tween the two needles an electrical
connection is established, the switch
is opened and the carrier is dis
charged into the receiver of the inter-
mediate station. The spacing between
the needles varies for each switch so it
is only necessary to attach a disk of
the proper diameter to a carrier to send
it automatically to the desired station.
To prevent operators from choking the
tube by transmitting carriers too rap
idly, time lock is placed on the send
ing apparatus allowing five, ten or fif-
teen seconds headway as may be de-
sired.
Pneumatic tubes, in recent years,
have become important features in re-
tail stores, taking the place of cash
boys They are used in the grain ele-
vators for lifting corn, wheat and
oats, and in sawmills and furniture fac
tories TO carry off the sawdust and
other refuse. They are common to
newspaper offices, and thousands of
miles Of railroad tracks are paralIeled
by the pipes which contain the COM
pressed air that operates the automatic
block signals. Their use is extending
rapidly and there seems to be little
doubt that in a few years they will
be used to carry not only mail and
kilograms. but bulky packages to all
parts Of large cities.
The TootjlSome Cocoauih.