HOISTING, CONVEYING AND STORING.
Allusion has been made to the stupendous buildings and works of the
ancients and of the middle ages; the immense multitude of workers and
great extent of time and labour employed in their construction; and how
the awful drudgery involved in such undertakings was relieved by the
invention of modern engineering devices--the cranes, the derricks, and
the steam giants to operate them, so that vast loads which required
large numbers of men and beasts to move, and long periods of time in
which to move them, can now be lifted with ease and carried to great
heights and distances in a few minutes by the hands of one or of a few
men.
But outside of the line of such undertakings there is an immense field
of labor-saving appliances adapted for use in transportation of smaller
loads from place to place, within and without buildings, and for
carrying people and freight from the lower to the upper stories of tall
structures. In fact the tall buildings which we see now in almost every
great city towering cloudward from the ground to the height of fifteen,
twenty and twenty-five stories, would have been extravagant and useless
had not the invention of the modern elevator rendered their highest
parts as easy of access as their lowest, and at the same time given to
the air space above the city lot as great a commercial value in feet and
inches as the stretch of earth itself.
Many of the “sky-scrapers” so called, are splendid monuments of the
latest inventions of the century.
It is by means of the modern elevator that the business of a whole town
may be transacted under a single roof.
In the multiplicity of modern human contrivances by which the sweat and
drudgery of life are saved, and time economised for worthier objects, we
are apt to overlook the painful and laborious steps by which they were
reached, and to regard with impatience, or at least with indifference,
the story of their evolution; and yet no correct or profound knowledge
of the growth of humanity to its higher planes can be obtained without
noting to what extent the minor inventions, as well as the startling
ones, have aided the upward progress.
For instance, consider how few and comparatively awkward were the
mechanical means before this century. The innumerable army of men when
men were slaves, and when blood and muscle and brain were cheap, who,
labouring with the beast, toiled upward for years on inclined ways to
lay the stones of the stupendous pyramids, still had their counterpart
centuries later in the stream of men carrying on their shoulders the
loads of grain and other freight and burdens from the shore to the holds
of vessels, from vessels to the shore, from the ground to high buildings
and from one part of great warehouses to another. Now look at a vessel
moved to a wharf, capable of holding fifty thousand or one hundred
thousand bushels of grain and having that amount poured into it in three
hours from the spouts of an elevator, to which the grain has been
carried in a myriad buckets on a chain by steam power in about the same
time; or to those arrangements of carriers, travelling on ropes, cords,
wires, or cables, by which materials are quickly conveyed from one part
of some structure or place to another, as hay and grain in barns or
mows, ores from mines to cars, merchandise of all kinds from one part of
a great store to another; or shot through pipes underground from one
section of a city or town to their destination by a current of air.
True, as it has before been stated, the ancients and later generations
had the wedge, the pulley, the inclined plane, the screw and the
windlass, and by these powers, modified in form and increased in size as
the occasion demanded, in the form of cranes, derricks, and operated by
animal power, materials were lifted and transported; but down to the
time of the practical and successful application of steam by Watt in the
latter part of the 18th century, and until a much later period in most
places in the world, these simple means actuated alone by men or animals
were the best means employed for elevating and conveying loads, and even
they were employed to a comparatively limited extent.
The century was well started before it was common to employ cups on
elevator bands in mills, invented by Oliver Evans in 1780, to carry
grain to the top of the mill, from whence it was to fall by gravity to
the grinding and flouring apparatus below. It was not until 1795 that
that powerful modern apparatus--the hydraulic, or hydrostatic, press was
patented by Bramah in England. The model he then made is now in the
museum of the Commissioner of Patents, London. In this a reservoir for
water is provided, on which is placed a pump having a piston rod worked
by a hand lever. The water is conveyed from the reservoir to a cylinder
by a pipe, and this cylinder is provided with a piston carrying at its
top a table, which rises between guides. The load to be carried is
placed on this table, and as the machine was at first designed to
compress materials the load is pressed by the rising table against an
upper stationary plate. The elevation of the table is proportionate to
the quantity of water injected, and the power proportionate to the
receptive areas of the pump and the cylinder. The first great
application of machines built on this principle was by Robert Stephenson
in the elevation of the gigantic tubes for the tubular bridge across the
Menai straits, already described in the chapter on Civil Engineering.
The century was half through with before it was proposed to use water
and steam for passenger elevators.
In 1852 J. T. Slade in England patented a device consisting of a drum to
be actuated by steam, water, or compressed air, around which drum ropes
were wound, and to which ropes were attached separate cages in separate
wells, to counterbalance each other, the cages moving in guides, and
provided with brakes and levers to stop and control the cages and the
movement of the drum. Louis T. Van Elvean, also of England, in 1858
invented counterbalance weights for such lifts. Otis, an American,
invented and patented in America and England in 1859 the first approach
to the modern passenger elevator for hotels, warehouses, and other
structures. The motive power was preferably a steam engine; and the
elevating means was a large screw placed vertically and made to revolve
by suitable gearing, and a cylinder to which the car was attached,
having projections to work in the threads of the screw. Means were
provided to start and to stop the car, and to retard its otherwise
sudden fall and stoppage.
Elevators, which are now so largely used to raise passengers and freight
from the lower to the upper stories of high edifices, have for their
motive power steam, water, compressed air, and electricity. With steam a
drum is rotated over which a hoisting wire-rope is wound, to which the
elevator car is attached. The car for passengers may be a small but
elegantly furnished room, which is carried on guide blocks, and the
stationary guides are provided with ratchet teeth with which pawls on
the car are adapted to engage should the hoisting rope give way. To the
hoisting rope is attached a counterbalance weight to partly meet the
weight of the car in order to prevent the car from sticking fast on its
passage, and also to prevent a sudden dropping of the car should the
rope become slack. A hand rope for the operator is provided, which at
its lower end is connected with a starting lever controlling the valves
of the cylinders into which steam is admitted to start the piston shaft,
which in turn actuates the gear wheels, by which movement the ropes are
wound around the drums.
In another form of steam elevator the drums are turned in opposite
directions, by right and left worms driven by a belt.
In the hydraulic form of elevator, a motor worked by water is employed
to lift the car, although steam power is also employed to raise the
water. The car is connected to wire cables passing over large sheaves at
the top of the well room to a counterbalancing bucket. This bucket fits
closely in a water-tight upright tube, or stand-pipe, about two feet in
diameter, extending from the basement to the upper story. Near this
stand-pipe in the upper story is placed a water supply tank. A pipe
discharges the water from the tank into the bucket, which moves up and
down in the stand pipe. There is a valve in the tank which is opened by
stepping on a treadle in the car, and this action admits to the bucket
just enough weight of water to overbalance the load on the car. As soon
as the bucket is heavier than the car it descends, and of course draws
the car upward, thus using the minimum power required to raise each
load, rather than, when steam is employed, the full power of the engine
each and every time. The speed is controlled by means of brakes or
clamps that firmly clasp wrought-iron slides secured to posts on each
side of the well room, the operator having control of these brakes by a
lever on the car. When the car has ascended as far as desired, the
operator steps upon another treadle in the car connected with a valve in
the bottom of the bucket and thus discharges the water into the
receiving tank below until the car is heavier than the bucket, when it
then of course descends. The water is thus taken from the upper tank
into the bucket, discharged through the stand-pipe into the receiving
tank under the floor of the basement and then pumped back again to the
upper tank, so that it is used over and over again without loss.
Various modifications have been made in the hydraulic forms. In place of
steam, electricity was introduced to control the hydraulic operation.
Again, an electric motor has been invented to be placed on the car
itself, with connected gearing engaging rack bars in the well.
Elevators have been contrived automatically controlled by switch
mechanisms on the landings; and in connection with the electric motor
safety devices are used to break the motor circuit and thus stop the car
the moment the elevator door is opened; and there are devices to break
the circuit and stop the car at once, should an obstruction, the foot
for instance, be accidentally thrust out into the path of the car frame.
Columns of water and of air have been so arranged that should the car
fall the fall will be broken by the water or air cushion made to yield
gradually to the pressure. So many safety devices have been invented
that there is now no excuse for accidents. They result by a criminal
neglect of builders or engineers to provide themselves with such
devices, or by a most ignorant or careless management and operation of
simple actuating mechanisms.
Between 1880 and 1890 there was great activity in the invention of what
is known as store service conveyors. One of the earliest forms, and one
which had been partly selected from other arts, was to suspend from a
rigid frame work connected to the floor, roof, or side of the building,
a long platform in the direction through the building it was desired the
road to run, giving this platform a slight inclination. On this platform
were placed tracks, and from the tracks were suspended trucks, baskets,
or other merchandise receptacles, having wheels resting on and adapted
to roll on the tracks. Double or single tracks could be provided as
desired. The cars ran on these tracks by gravity, and considerable
ingenuity was displayed in the feature alone of providing the out-going
and returning inclined tracks; in hand straps and levers for raising and
lowering the carriage, part or all of it, to or from the tracks, and in
buffers to break the force of the blow of the carriages when arriving at
their stopping places.
Then about 1882-83 it was found by some inventors if moderately fine
wires were stretched level, and as tight as possible, they would afford
such little friction and resistance to light and nicely balanced wheels,
that no inclination of the tracks was necessary, and that the carriages
mounted on such wheels and tracks would run the entire length of a long
building and turn corners not too sharp by a single initial push of the
hand. In other arrangements a carrier is self-propelled by means of a
coiled spring on the carrier, which begins its operation as soon as the
carrier is given a start; and to meet the exhausted strength of such
spring, coiled springs at different points on the line are arranged to
engage and give the carrier an additional push. Before the carrier is
stopped its action is such as to automatically rewind its spring.
A system of pneumatic transmission was invented, by which a carrier is
caused to travel through a tube by the agency of an air current, created
therein by an air compressor, blower, or similar device. The device is
so arranged that the air current is caused to take either direction
through the tube; and in some instances gravity may be used to assist a
vacuum formed behind the carrier. The tube is controlled at each end by
one or more sliding gates or valves, and the carrier is made to actuate
the gates, and close the one behind it, so that the carrier may be
discharged without permitting the escape of the air and consequent
reduction of pressure.
An interesting invention has been made by James M. Dodge of Philadelphia
in the line of conveyors, whereby pea coal and other quite heavy
materials introduced by a hopper into a trough are subjected to a
powerful air blast which pushes the material forward; and as the trough
is provided with a series of frequently occurring slots or perforations
open to the outer air and inclined opposite the direction of travel, the
powerful current from the blower in escaping through such outlets tends
to lift or buoy the material and carry it forward in the air current,
thereby greatly reducing frictional contact and increasing the impelling
operation. The inventor claims that with such an apparatus many tons of
material per hour may be conveyed with a comparatively small working air
pressure.
In order that a conveyor carriage may be automatically switched off at a
certain place or station on the line, one mode adopted was to arrange at
a gate or station a sort of pin or projection or other deflector to
engage some recess or corresponding feature on the carriage, so as to
arrest and turn the carriage in its new direction at that point. Another
mode was the adoption of electro-magnets, which would operate at a
certain place to arrest or divert the carriage; and in either case the
carriage was so constructed that its engaging features would operate
automatically only in conjunction with certain features at a particular
place on the line.
Signals have been also adopted, in some cases operated by an electric
current, by which the operator can determine whether or not the
controlling devices have operated to stop the carrier at the desired
place. By electric or mechanical means it is also provided that one or
more loop branches may be connected with or disconnected from the main
circuit.
The “lazy tongs” principle has been introduced, by which a long
lazy-tongs is shot forth through a tube or box to carry forward the
carriage; and the same principle is employed in fire-escapes to throw up
a cage to a great height to a window or other point, which cage is
lowered gently and safely by the same means to the ground. Buffers of
all kinds have been devised to effect the stoppage of the carrier
without injury thereto under the different degrees of force with which
it is moved upon its way, to prevent rebounding, and to enable the
carrier to be discharged with facility at the end of its route.
Among the early mechanical means of transporting the carriage was an
endless cable moved continuously by an engine, and this adoption of
cable principle in store service was co-eval with its adoption for
running street cars. Also the system of switching the cars from the main
line to a branch, and in different parts of a city, at the same time
that all lines are receiving their motive power from the main line,
corresponds to the manner of conveying cash to all parts of a building
at the same time from many points.
To the great department store or monstrous building wherein, as we have
said, the whole business of a town may be transacted, the assemblage and
conjoint use of elevators and conveyors seem to be actually necessary.
A very useful and important line of inventions consists in means for
forming connections between rotary shafts and their pulleys and
mechanisms to be operated thereby, by which such mechanism can be
started or stopped at once, or their motion reversed or retarded; or by
which an actuating shaft may be automatically stopped. These means are
known as _clutches_.
They are designed often to afford a yielding connection between the
shaft and a machine which shall prevent excessive strain and wear upon
starting of the shaft. They are also often provided with a spring
connection, which, in the rotation of the shaft in either direction,
will operate to relieve the strain upon the shaft, or shafts, and its
driving motor. Safety clutches are numerous, by which the machine is
quickly and automatically stopped by the action of electro-magnets
should a workman or other obstruction be caught in the machinery.
Electric auxiliary mechanism has also been devised to start or stop the
main machine slowly, and thus prevent injury to small or delicate parts
of complicated machines, like printing presses for instance. Clutches
are arranged sometimes in the form of weights, resembling the action of
the weights in steam governors, whereby centrifugal action is relied
upon for swinging the weights outward to effect a clutching and coupling
of the shaft, or other mechanism, so that two lines of shafting are
coupled, or the machine started, or speeded, at a certain time during
the operation. In order to avoid the great mischief arising sometimes
from undue strain upon and the breaking of a shaft, a weak coupling
composed of a link is sometimes employed between the shaft and the
driven machine, whereby, should the force become suddenly too great, the
link of weaker metal is broken, and the connection between the shaft
thereby destroyed and the machine stopped.
To this class of inventions, as well as to many others, the phrase,
“labour-saving”, is applied as a descriptive term, and as it is a
correct one in most instances, since they save the labour of many human
hands, they are regarded by many as detrimental to a great extent, as
they result in throwing out of employment a large number of persons.
This derangement does sometimes occur, but the curtailment of the number
of labourers is but temporary after all.
The increased production of materials, resulting from cheaper and better
processes, and from the reduced cost of handling them, necessitates the
employment of a larger number of persons to take care of, in many ways,
the greater output caused by the increased demand; the new machinery
demands the labour of additional numbers in its manufacture; the
increase in the size and heights of buildings involves new modes of
construction and a greater number of artisans in their erection; new
forms of industry springing from every practical invention which
produces a new product or results in a new mode of operation,
complicates the systems of labour, and creates a demand for a large
number of employers and employees in new fields. Hence, it is only
necessary to resort to comparative, statistics (too extensive to cite
here) to show that the number of unemployed people in proportion to
the populations, is less in the present age than in any previous
one. In this sense, therefore, inventions should be classed as
labour-_increasing_ devices.