In Ancient Times
The first elevation and transport devices were
levers, pulleys, rollers and planes with an inclination. Great
feats of construction with this kind of equipment required huge
numbers of people. We have an example in the construction of the
Keops Pyramids (2,500 BC) which are 147 metres high and made of
stone blocks each measuring 9 x 2 x 2 cubic metres and each one
weighing 90 tonnes. Their construction went on for 20 years and
almost one hundred thousand labourers were permanently employed
in the task.
From pulley and cable
to the crane drum
Around 1510 BC, the wheel which had previously
only been used in carts, was given new uses. The potter’s
wheel and distaffs were mechanical devices which took advantage
of forces to do work and to do so with less effort. Thanks to
this, the resistance due to friction was reduced and limited to
that found between the shaft and the main bearing. The cable pulley
was a major breakthrough in the transformation of forces while
avoiding friction in the rope. It is not clear if the cable pulley
was first used in Mesopotamia or Egypt in the form of a simple
pulley.
Around 700 BC Greek mechanics developed the technique
of breaking down force vectors with hoists made of sets of pulleys.
A hoist has a fixed pulley and a second one attached to the object
to be moved. A rope runs through it from a starting point, first
through the mobile pulley and then around the fixed pulley. By
pulling on the free end the load moves one half of the distance
that corresponds to the movement along the free end.
The Greco-Roman period (10th Century BC to 5th
Century BC) was a great leap forward in the evolution of elevation
technology. A key element in elevation is the composite pulley.
Its origin can be traced to Classical Greece and to Euripides
(480- 406 BC).
The thinker Archimedes (287 – 212 BC) apart
from discovering the Archimedean screw -the principle on which
elevators and belts of today is based- developed an elevating
device that used hemp ropes and pulleys manipulated by men.
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The great step forward
in mechanics
In the 3rd Century BC, Archimedes discovered the
laws of leverage. This Greek who lived in Syrac, created a theoretical
system based on the multiplication of force that is achieved in
the application of a lever, the effect of a wedge, the fulcrum
and the use of a sloping plane and pulley; these are phenomena
that had been evident and which had been taken advantage of for
centuries. He developed an extensive theory in relation to hoists
with multiple pulleys and the transmission of forces that can
do work in ratios of 2:1, 3:1(hoist with a set of 3 pulleys) and
5:1 (hoist with a set of 5 pulleys).
During the Roman Empire, when Titus was Emperor
in 80 AD, twelve huge lifts were installed to elevate the gladiators
and beasts onto the combat field. After the fall of the Roman
Empire, lifts seemed to disappear for a long period.
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The Middle Ages
Leonardo da Vinci was interested in tackling complex
questions and tended to search for a technical solution to problems.
To this end, he created a mobile crane to facilitate construction
tasks where lifting heavy loads are involved. His crane was mounted
on a kind of vehicle and was commanded from the upper level by
way of a cable under tension; it was a hand-driven mechanical
system which provided transmission by way of indented cogs and
wheels.
Georg Bauer (1490- 1565) was a doctor who worked
in the mining areas of Saxony. His treatise De re metallica, published
in 1556, is considered to be an exact guide of the systems used
in the High Middle Ages in a very traditional industry. ln De
re metallica we find an illustration of an elevating mechanism
for a mine. Mention is made of indented wheels and cogs and chains
moved by horses. There are no significant differences between
this system and primitive prototypes except for a dump car that
slid along guide rails.
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The first lift
In 1830 a cargo lift operated by a machine came
into service in Derby England. In 1840 we find in West Riding,
Yorkshire winches being used for the hand-operated lifting of
weights. This technique was used for a number of varied elevating
and transport operations including the elevation of earth moved
during railway tunnel excavations.
The main cable drum with a diameter of 3.5 to 5
metres, around which horses worked, was eventually substituted
by a vertically positioned steam-driven winch. This more advanced
winch was characterised by its low steam pressure and sole-cylinder
structure.
Mention must be made of the Teagle lift developed
in England in 1845. This hydraulic-operated system already included
the concept of a traction pulley with a counterweight, an element
found in the great majority of modern lifts. It was directly operated
by the users themselves which manually engaged the cable from
the cabin.
In 1854 Elisha Graves Otis offered a public demonstration
from the Crystal Palace in New York, elevating the lift up to
a certain height and cutting the support cables in order to prove
the safety of the machine.
This hydraulic lift came complete with a safety
system which involved a cabin fitted with ratchets which -in case
of accidental breakage of the cable- would latch onto catches
embedded into the walls of the lift well.
On March 23, 1857 the first lift for people was
installed at the E. V. Haughwout & Co. Department Stores in
New York. The steam-driven lift serviced a building with five
floors and came complete with elevation machinery suitable for
450 Kg at 0.2 metres/ second.
In 1867 a Frenchman, Leon Edoux presented at the
Paris Universal Exposition an elevating device which made use
of high water pressure to raise a cabin mounted on hydraulic piston.
The Edoux lift had was well received worldwide,
particularly when, greater speeds and distances became available.
The system was improved and was referred to the as an indirect
operation system; here the embolus or stopper mechanism does not
directly move the cabin; rather, it moved a series of pulleys
fixed onto a traction path and had a revolving drum that would
coil up and uncoil various cables from which the cabin was suspended.
Simultaneously, Europe ventured in to the vertical
elevation industry in 1874 with the foundation of the Schindler
Company which in 1876 installed the first lift in London’s
General Post Office.
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The hydraulic lift
The hydraulic lift was used for the first time
in 1878, where water was used instead of steam in order to simplify
installations and obtain greater speeds over longer trajectories.
Hydraulic lifts were constantly improved until
considerable heights and lifts were obtained. In 1908, a lift
was installed at New York’s City Investing Building and
could deal with a load of 1360 Kg at a speed of 3 m/sec for a
total height of 108 m.
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Electric traction
The first electric lift appeared in the Demarest
Building in New York. It was a direct modification of the early
steam-driven lift with revolving drum. Instead of steam, electricity
from a continuous current motor was used. This lift continued
in operation until the building’s demolition in 1920. The
first lift with electric call buttons was installed in 1894.
The electric lift enjoyed enormous success right
from the beginning as it was cheaper to install and operate but
it had the disadvantage of being rather imprecise with its stopping
positions. This drawback was overcome with the installation of
Ward Leonard speed-regulating units still in use today.
In 1900 cable-led manoeuvres were substituted by
button operated functions. The Ward Leonard system was introduced
between 1910 and 1930 and speeds of up to 2 m/sec were obtained.
It was the dawn of the modern lift.
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Operating systems
In early steam-driven or hydraulic lifts, the operational
mechanism was a cable the ran up and down the whole distance of
the lift well and that activated a valve positioned at the bottom
of the lift well. To go up, the cable was pulled downwards to
introduce steam or water into the pressurised circuit. To go down,
the cable was pulled upwards to expel steam or water and hence
causing the platform to be lowered.
This system, which consisted of pulling the cable
contrary to the desired direction of movement, had an advantage:
that both the lowest position and the highest one made use of
a “stopping ball.” Hence when the lift was at the
lowest position, any attempt to keep going down was thwarted by
pulling the cable upwards thereby releasing a metallic ball into
a round slot located in the cabin interior. The ball locked into
a hole, effectively halting the cabin on the appropriate floor.
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Automatic operating
system
The use of control panel with buttons inside the
cabin was used in office buildings from the early 1880s to 1920.
Similarly, in the period 1880 to 1920, this operating system was
extended to residential buildings in the United Status and became
to be known as “Simple Automatic System”. Given that
the traffic was low, a full-time operator was not required and
hence there was a need for an automatic system quite similar to
those we have in service today. It consisted of a series of buttons
in the cabin and on each floor in such a way that there is priority
operation of the cabin from within. When the order given inside
the cabin has finalised, the lift is available for service on
any floor where it has access. This system is used today in lifts
with low traffic where users prefer to wait and have exclusive
use of the cabin space.
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Signal control
As both the height of buildings increased as well
as their speed (up to 3.5 m/s), the need Grew for an efficient
operation system which would stop the cabin in the precise position.
This was introduced in the beginning of 1920 in the so-called
signal control. It required an operator who would press buttons
and establish a regime of operating orders; the system would automatically
establish accelerations, responses to calls from other floors,
decelerations and the necessary adjustments to be level with the
floor. The operator did not know which orders had come in until
the braking process had been activated.
Collective operating systems allow calls to be stored in a memory
in both directions, up or down; this enables the lift to finish
a particular route and to automatically revert to the opposite
direction to service calls that have been previously registered.
There is no need for an operator in this system.
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Group-based automatic
operating systems
The end of the 1940s saw the advent of a system
based on electronic circuits which measured the number of calls,
the time they took and then automatically combined these data
with other data to programme and operate lifts in a group. Such
a system was installed in the UN building in New York in 1949.
Months later, the first electronic system applied to the lift
doors to protect passengers became a reality.
Looking back at the history of lifts, we can observe that two
parallel technologies have developed side by side. On the one
hand we have signal control which needed an operator which was
desirable for large buildings with a large traffic flow; on the
other we have the collective operating systems which did not require
an operator but which were useful in residential buildings with
generally low traffic. The inventor responsible was the Development
Engineer at the Otis Elevator Company, William Bruns. By using
electronic and automatic circuits it was possible to programme
efficient manoeuvres from a vertical traffic point of view.
From the early 50s up to the present, all lift companies have
developed programmed orders. The Otis Elevator Company introduced
the programmes known as: Autotronic (4 and 6), the Basic Autotronic
with Multiple Zoning, VIP 260 and the Elevonic programmes. Schindler
developed the equipment series known as Auto Signamatic, 1090,
1092IC, Aconic, Supermatic, Transitronic and Miconic. Westinghouse
introduced the Selectomatic families (4 and 6 Pattern and Mark
IV and V). Dopver sytems were termed Traflomatic and finally for
the Montgomery series, the brand developed was Miprom.
In 1986 the variable frequency system for high-speed lifts was
introduced, a major advance being that there is a considerable
saving of energy. Two years later, motor lineal technology became
available. In this mode, the counterweight system is included
and the need for a separate machine room is eliminated and is
therefore more economical and space-saving.
Today, at the end of the 20th Century, there have been great advances
in lift technology. However there is still a series of questions
to be contemplated in an updated lift service such as:
• Greater operating speeds (up to
15 m/sec)
• Greater user comfort; in other words, smoother rides and
no jolts.
• More exact levelling up when stopping at floors independent
of the loads carried.
• Reduction of waiting times at floors and optimisation
of traffic flows.
• Maximum safety for users and in general operation.
• Maximum reliability in service performance.
Throughout the 20th Century, the three
continents have played a crucial role in lift Technologies with
such advances as:
• Lifts without a reducer.
• Control system with memory for groups of lifts.
• Microprocessor in control systems for groups of lifts.
• Variable control frequency systems and tensions.
• Motor lineal technology without machine rooms.
• Modular control system.
• Permanent magneto-motor.
• Etc.
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