ELEVATOR OR LIFT
Ø DEFINITION
An elevator (US, Canada and Japan) or
lift (Commonwealth countries) is a type of vertical transportation device that moves "people or goods between floors (levels, decks) of a building,
vessel, or other structure. Elevators are typically powered by electric motors that drive
traction cables and counterweight
systems like a hoist, although
some pump hydraulic
fluid to raise a
cylindrical piston like a jack.
In agriculture and manufacturing,
an elevator is any type of conveyor
device used to lift materials
in a continuous stream into bins or silos. Several
types exist, such as the chain and bucket elevator, grain auger screw conveyor
using the principle of Archimedes' screw, or the chain and paddles or
forks of hay elevators. Languages other
than English may have loanwords
based on either elevator or lift. Because of wheelchair access laws, elevators
are often a legal requirement in new multistory buildings, especially
where wheelchair ramps would be impractical.
Ø TYPES OF ELEVATORS
- Traction elevators
Geared traction machines are driven by AC or DC electric motors. Geared machines use worm
gears to control mechanical
movement of elevator cars by "rolling"
steel hoist opes over a drive sheave which is attached
to a gearbox driven by a high-speed motor. These machines
are generally the best option for basement or overhead traction
use for speeds up to 3 m/s (500
ft./min).
Historically, AC motors were used for single or double-speed elevator
machines on the grounds of cost
and lower usage applications
where car speed and passenger comfort were less of an issue, but for higher
speed, larger capacity elevators, the need for infinitely
variable speed control over the
traction machine becomes an issue. Therefore, DC machines powered by an AC/DC motor generator were the preferred solution. The MG set also typically powered
the relay controller of the elevator, which has the added advantage of
electrically isolating the elevators
from the rest of a building's
electrical system, thus eliminating the transient
power spikes in the building's
electrical
supply caused by the motors
starting and
stopping (causing lighting to dim every time the elevators
are used for example), as well as interference to other electrical equipment caused
by the arcing of the relay contactors
in
the control system.
The widespread availability of variable
frequency AC drives has allowed AC motors to be used universally, bringing
with It the advantages of the older motor-generator, DC-based
systems, without the penalties in terms of efficiency and complexity.
The older MG-based installations are gradually being replaced in older buildings due to their poor energy efficiency.
Gearless traction machines
are low-speed (low-RPM), high-torque electric motors powered either
by AC or DC. In this case, the drive sheave is directly attached to the end of the
motor.
Gearless
traction elevators can reach speeds
of up to 20 m/s (4,000 ft./min), A brake is mounted
between the motor and gearbox or between the motor and drive sheave or at the end of
the drive sheave
to hold the elevator stationary at a floor.
This brake Is usually an external drum type and is actuated by spring force and held open electrically; a power failure will cause the brake to engage and prevent the elevator from falling (see inherent
safety and safety engineering). But it can also be some form of disc type like 1 or more calipers over a disc in one end of the motor shaft or drive sheave which is used in high speed, high rise and large capacity elevators with machine rooms(an
exception is the Kone MonoSpace's EcoDisc
which is not high speed, high rise and large capacity and is machine room less but it uses the same design as is a thinner
version of a conventional gear1ess traction machine) for braking power, compactne0ss and redundancy (assuming
there's at least 2 calipers on the disc), or
1 or more disc brakes with a single caliper at one end of the motor shaft or
drive
sheave which is used in
machine room less elevators for compactness, braking
power,
and redundancy (assuming there's 2 brakes
or more).
In each case, cables are attached to a hitch plate on top of
the cab or
may be “underslung” below a cab, and then looped over the drive sheave to a counterweight attached to the opposite end of the cables which reduces the amount of power
needed to move the cab. The counterweight is located in the hoist-way and rides a separate railway system; as the car goes up, the counterweight goes down,
and vice versa. This action is powered by the traction machine which is directed by the controller, typically a relay logic or computerized device
that directs starting, acceleration, deceleration and stopping of the elevator cab. The weight of the counterweight is typically equal to the weight of the elevator cab plus 40-50%
of the capacity of the elevator. The grooves in the drive sheave are specially
designed to prevent the cables from slipping. “Traction” is provided to the ropes by the grip of
the grooves in the sheave, thereby the name. AB the ropes age
and the traction
grooves wear, some traction is lost and the ropes must be replaced and the sheave
repaired or replaced. Sheave and rope wear may be significantly reduced by ensuring that all ropes have equal tension,
thus sharing the load evenly. Rope tension
equalization may be achieved using a rope tension gauge, and is a
simple
way to extend the lifetime of the sheaves
and ropes.
Elevators with more than 30 m (98 ft.) of travel have a system called compensation. This is a separate set of cables or
a chain attached to
the bottom of
the counterweight and the bottom of
the elevator cab. This makes it easier to
control the elevator, as
it compensates for the differing
weight of cable between the hoist and the cab. If the elevator
cab Is at the top of
the hoist-way, there is a
short length of
hoist
cable above the car and a long length of compensating cable below the car and vice versa for the counterweight. If the compensation system uses cables, there will be an additional sheave in the pit below the
elevator, to guide the cables. If
the compensation system
uses chains, the chain is guided by a bar mounted
between the counterweight railway lines.
- Regenerative drives
Another energy-saving improvement is the regenerative drive, which works analogously
to regenerative braking in vehicles, using the elevator's electric
motor as a generator to capture
some of the gravitational potential
energy of descent of
a full cab (heavier than its counterweight) or ascent of an empty cab (lighter than its counterweight) and
return it to the building's
electrical system.
- Hydraulic elevators
- Conventional hydraulic elevators. They use an underground hydraulic cylinder. are quite common for low level buildings with two to five floors (sometimes but seldom up to six to eight floors), and have speeds of up to 1 m/s (200 ft./min). For higher rise applications. a telescopic hydraulic cylinder can be used.
- Hole-less hydraulic elevators were developed in the 1970s, and use a pair of above ground cylinders, which makes it practical for environmentally or cost sensitive buildings with two. three, or four floors.
- Roped hydraulic elevators use both above ground cylinders and a rope system, allowing the elevator to travel further than the piston has to move.
The low mechanical complexity of hydraulic elevators in comparison to traction elevators makes them ideal for low rise, low traffic installations.
They are
less energy efficient as
the pump works against gravity
to push the car and Its passengers upwards; this energy
ls lost when the car descends on its own weight. The high current
draw of the pump when starting
up also places higher demands on a building's electrical system. There are also environmental concerns
should the lifting cylinder leak fluid into the ground.
The modem generation
of low-cost, machine room-less traction elevators
made possible by advances
in miniaturization of the traction
motor and control systems challenges the supremacy of
the hydraulic elevator
in their traditional market niche.
- Electromagnetic propulsion
Cable-free elevators using electromagnetic propulsion, capable of
moving both vertically and horizontally, have been developed by German engineering firm Thyssen Krupp for use in high rise, high density buildings.
- Climbing elevator
A climbing elevator is a self-ascending elevator with its own propulsion. The propulsion can be done by an electric
or a combustion engine. Climbing elevators
are used in guyed masts or towers, in order to make easy access to parts of these constructions,
such as flight safety lamps for
maintenance.
An example would be the Moonlight
towers in Austin,
Texas, where the elevator
holds only one person and
equipment for maintenance. The Glasgow Tower-an observation
tower in Glasgow,
Scotland-also makes use of two climbing elevators.
- Pneumatic elevator
An elevator of this kind uses a vacuum on top of the cab and a valve
on the top of the "shaft" to move the cab upwards
and closes the valve in order to keep the cab at
the same level. A diaphragm or a piston is used as a "brake", if
there's a sudden increase in pressure above the cab. To go
down, it opens the valve so that
the air can pressurize the top of the "shaft", allowing the cab to go down by
its own weight.
This also means that in case of
a power failure, the cab will automatically
go down. The "shaft” is made of acrylic, and is always
round due to
the shape of
the vacuum pump turbine. In order to
keep
the air inside of the cab, rubber seals are used. Due to technical limitations, these elevators have a
low capacity, they usually allow 1-3 passengers and up to 525 lbs.
Ø Controlling elevators
- Manual controls
In the first half of the twentieth
century, almost all elevators had no automatic
positioning of the floor
on which
the cab would stop. Some of
the older freight elevators were controlled by
switches operated by pulling on adjacent ropes. In general, most elevators before
WWII were manually controlled by elevator
operators using a rheostat connected
to the motor. his rheostat (see picture) was enclosed within a cylindrical container about the size and shape of
a cake. This was mounted
upright or sideways on
the cab wall and operated via a projecting handle, which was able to slide around the top half of the cylinder.
The elevator motor was located at the top of the shaft or beside the bottom of the shaft. Pushing the
handle forward would cause the cab to
rise; backwards would make it sink. The harder the pressure,
the faster the elevator would move. The handle also served as a dead man switch: if the operator let go of the handle, it would return to
its upright position, causing the elevator cab to stop. In time, safety inter1ocks would
ensure that the inner and outer doors were closed before the elevator was allowed to move.
This lever would
allow some control over the energy supplied to the motor and so enabled the
elevator to be accurately positioned -
if the operator was
sufficiently skilled. More typically, the
operator would have to "jog" the control, moving the cab in small increments until the elevator was reasonably close to the landing point. Then the operator would direct the outgoing and incoming passengers to "watch the step".
Automatic elevators began to appear as ear1y as the 1930s, their development being hastened by striking elevator
operators which brought
large cities dependent on skyscrapers (and
therefore their elevators) such as New York and Chicago
to their knees. These electromechanical systems used relay logiccircuits of increasing complexity to control the speed,
position and door operation of an elevator or bank of elevators.
The Otis Autotronic system of the early 1950s brought
the ear1iest predictive systems which could anticipate traffic patterns within a building to deploy elevator
movement in the most efficient manner. Relay-controlled elevator systems remained common until the 1980s and their gradual replacement with solid-state, microprocessor-based controls are now the industry
standard. Most older, manually• operated elevators
have been retrofitted with automatic or semi-automatic controls. Using the emergency call button in an
elevator. There is Braille text for
visually impaired people and the button
glows
to alert a hearing impaired person that the bell is ringing
and the call is being placed.
- General controls
A typical modem passenger
elevator will have:
- Outside the elevator, buttons to go up or down (the bottom floor only has the up button, the top floor only has the down button, and every floor in between has both)
- Space to stand in, guardrails, seating cushion (luxury)
- Overload sensor-prevents the elevator from moving until excess load has been removed. It may trigger a voice prompt or buzzer alarm. This may also trigger a “full car” indicator, indicating the car's inability to accept more passengers until some are unloaded.
- Electric fans or air conditioning units to enhance circulation and comfort.
- A control panel with various buttons. In many countries, button text and icons are raised to allow blind users to operate the elevator; many have Braille text besides. Buttons include:
- Call buttons to choose a floor. Some of these may be key switches (to control access). In some elevators, certain floors are inaccessible unless one swipes a security card or enters a passcode (or both).
- Door open and door close buttons
The operation of
the
door open button fs transparent, immediately opening and holding the door. typically, until a timeout occurs
and the door closes. The operation of the door close button
is less transparent, and it often appears to
do nothing, leading to frequent but incorrect reports
that the door close button is a placebo
button: either not wired up at all, or inactive in normal service. Working
door open and door close buttons are required by code in many
jurisdictions, including the United States, specifically for emergency operation: in independent mode, the door open and door close buttons
are used to manually open or close the door. Beyond this, programming varies significantly with some door close buttons
immediately closing the. door, but in other cases being delayed by an overall timeout, so
the door cannot be closed until a few seconds after opening. In this case (hastening normal closure), the door close button has no effect. However, the door close button will cause a hall call to be ignored (so the door won't reopen). and once the
timeout has expired, the door close will immediately close the door, for example to
cancel
a door open push. The minimum timeout for automatic door closing in
the US is 5 seconds, which is
a noticeable delay if
not overridden.
- An alarm button or switch, which passengers can use to warn the premises manager that they have been trapped in the elevator.
- A set of doors kept locked on each floor to prevent unintentional access into the elevator shaft by the unsuspecting Individual. The door is unlocked and opened by a machine sitting on the roof of the car, which also drives the doors that travel with the car. Door controls are provided to close Immediately or reopen the doors, although the button to close them is often disabled during normal operations, especially on more recent elevators. Objects in the part of the moving doors will either be detected by sensors or physically activate a switch that reopens the doors. Otherwise. the doors will dose after a preset lime. Some elevators are configured, to remain open at the floor until they are required to move again.
- Elevators in high traffic buddings often have a “nudge” function (the Otis Autotronic system first introduced this feature) which will close the doors at a reduced speed. and sound a buzzer if the "door open” button is being deliberately held down. or if the door sensors have been blocked for too long a time.
- A stop switch (not allowed under British regulations) to half the elevator while in motion and often used to hold an elevator open while freight is loaded. Keeping an elevator stopped for too long may set off an alarm. Unless local codes require otherwise, this will most likely be a key switch.
- An elevator telephone, which can be used (in addition to the alarm) by a trapped passenger to call for help. This may consist of a transceiver, or simply a button.
- Hold button: This button delays the door closing timer, useful for loading freight and hospital beds.
- Call cancellation: A destination floor may be deselected by double clicking.
- Access restriction by key switches, RFID reader, code keypad, hotel room card, etc.
- One or more additional sets of doors. This is primarily used to serve different floor plans: on each floor only one set of doors opens. For example, in an elevated crosswalk setup, the front doors may open on the street level, and the rear doors open on the crosswalk level. This is also common in garages. rail stations, and airports. Alternatively, both doors may open on a given floor. This is sometimes timed so that one side opens first for getting off, and then the other side opens for getting on. to improve boarding/exiting speed. This is particularly useful when passengers have luggage or carts, as at an airport, due to reduced maneuverability
- In case of dual doors, there may be two sets of door open and door close buttons, with one pair controlling the front doors, from the perspective of the console, typically denoted <> and ><, with the other pair controlling the rear doors, typically denoted with a line in the middle, <|> and >|<, or double lines. I<>l and >ll<. This second set is required in the US if both doors can be opened at the same landing so that the doors can both be controlled in independent service.
- Security camera
- Plain walls or mirrored walls.
- Glass windowpane providing a view of the building Interior or onto the streets.
Other controls, which are generally
inaccessible to the public (either because they are key switches, or because they are kept behind a locked panel), include:
Fireman's service, phase II key switch
Switch to enable or disable the elevator.
Fireman's service, phase II key switch
Switch to enable or disable the elevator.
- An inspectors switch, which places the elevator in Inspection mode (this may be situated on top of the elevator)
- Manual up/down controls for elevator technicians. to be used in inspection mode, for example.
- An independent service/exclusive mode (also known as "Car Preference"), which will prevent the car from answering to hall calls and only arrive at floors selected via the panel. The door should stay open while parked on a floor. This mode may be used for temporarily transporting goods.
- Attendant service mode
- Large buildings with multiple elevators of this type also had an elevator dispatcher stationed In the lobby to direct passengers and to signal the operator to leave with the use of a mechanical "cricket" noisemaker.
Elevators are typically controlled from the outside by a call box, which has up and down buttons. at each stop. When pressed at a certain floor, the button (also known as a "hall call” button) calls the elevator to pick up more passengers. If the particular elevator is currently serving traffic in a certain direction, it will only answer calls in the same direction unless there are no more calls beyond that floor
In a group of two or more elevators,
the call buttons
may be linked to
a central dispatch
computer. such that they illuminate and cancel together. This is done to
ensure
that only one car Is called at
one time.
Key switches may be installed on the ground floor so that the elevator can be remotely switched on or off from the outside.
In destination control
systems, one selects the intended destination floor (in
lieu of pressing "up" or "down") and is then notified which elevator will serve their request.
Ø Elevator algorithm
The elevator algorithm, a simple algorithm
by which a single elevator
can decide where to stop, is summarized as follows.
- Continue traveling in the same direction while there are remaining requests in that same direction.
- If there are no further requests in that direction, then stop and become Idle, or change direction if there are requests in the opposite direction.
Ø Destination
control system
Some skyscraper buildings and other
types of installation feature a
destination operating panel
where a passenger
registers their floor calls before entering
the car. The system lets them know which car to wait for, instead of
everyone boarding the next car. In this way, travel time is reduced
as the elevator makes fewer stops for
Individual passengers, and the computer distributes adjacent stops to different cars in the bank. Although travel time is reduced,
passenger waiting times may be longer as they will not necessarily be allocated the next car to depart. During the down peak
period the benefit
of destination
control will be limited as passengers have a common destination.
It can also improve accessibility, as a mobility-impaired
passenger can move to his or her designated car in advance.
The idea of destination control was originally conceived
by Leo Port from Sydney in 1961, but at that lime elevator controllers were implemented
in relays and were unable to
optimize the performance
of destination
control allocations.
The system was first pioneered
by Schindler Elevator in 1992 as the Miconic 10. Manufacturers of
such systems claim that average traveling time can be reduced by up to 30%.
However, performance enhancements cannot be generalized as the benefits
and limitations of the system are dependent
on many factors. One problem
is that the system is subject to gaming. Sometimes,
one person enters the destination tor a large group
of people going to
the same floor. The dispatching algorithm Is usually unable to
completely cater for the variation, and latecomers may find the elevator they are assigned
lo is already full. Also, occasionally, one person may press the floor multiple limes. This is common with up/down
buttons when people believe this to be an effective way to hurry elevators.
However, this will make the computer think multiple people
are waiting and will allocate empty cars to serve this one person.
To prevent this problem, in one Implementation of destination control,
every user is giver, an RFID card, for identification and tracking, so that the system
knows every user call and can
cancel the first call if the passenger
decides to travel to another destination, preventing empty calls. The newest Invention knows even where people are located and how many on which floor because
of their Identification,
either for the purposes of evacuating the building or for
security reasons. Another way to prevent this issue is to treat everyone traveling from one floor to another as one group and to allocate only one car for that group.
The same destination scheduling concept can also be applied to public transit such as in group rapid transit.
Ø Safety
On 26 February 2014, the European union released their adoption of
safely
standards through a
directive notification.
- Cable - borne elevator
Statistically speaking, cable-borne elevators are extremely safe. Their safety record is unsurpassed by any other vehicle system. in 1998, it was estimated that approximately eight millionths of one percent (1 In 12 million)
of elevator rides result in an anomaly,
and the
vast majority of these were minor things such as the doors falling
to open. Of the 20 to
30 elevator-related deaths each year, most of them are maintenance-related- for
example, technicians leaning too far in to the shaft or getting caught between
moving parts, and most of the rest are attributed to
other kinds of accidents, such as people stepping blindly through doors that open into empty shafts
or being strangled by scarves
caught in the doors. M in fact, prior to the September
11th terrorist attacks. the only known free-fall incident in a
modem
cable-borne elevator happened
in 1945 when
a B-25 bomber struck the Empire
State Building in fog, severing the cables of
an elevator cab, which
fell from the 75th floor all the way to the bottom of the building, seriously Injuring (though not kiting) the sole occupant - the elevator operator. However, there was an incident
in 2007 at a Seattle children's hospital, where a ThyssenKrupp ISIS machine-room-less elevator free-fell until the safety brakes were engaged. This was due to a flaw in the design where the cables were connected at one common point, and the kevlar ropes had a
tendency to overheat and cause slipping (or, in this case, a free-fall). While it is possible
(though extraordinarily unlikely)
for an elevator’s cable to
snap, all elevators in the modem era have been fitted
with several safety devices
which prevent the elevator from simply
free-falling
and crashing. An elevator cab is typically
borne by 2 to 6 (up to 12 or more in high rise installations) hoist cables or
belts, each of which is capable on its own of supporting the full load of
the
elevator plus twenty-five percent more weight. In addition, there is a device which detects whether the elevator is descending faster than its maximum designed speed; If this happens, the device causes copper
(or silicon nitride
in high rise Installations} brake shoes to clamp down along the vertical rails in the shaft, stopping the elevator quickly, but not so abruptly as to cause injury. This device is
called
the governor, and was invented by Elisha Graves Otis. In addition, an oil/hydraulic or spring
or polyurethane
or telescopic oil/hydraulic buffer or a combination (depending on
the travel height and travel speed) Is installed
at the bottom of
the shaft (or in the bottom of the cab and sometimes also in the top of the cab or
shaft) to somewhat cushion any impact. However, In Thailand
in November 2012, a woman was killed in a free falling elevator, in what was reported as the ''first legally recognized death caused by a falling lift.
Hydraulic elevators :-
Past problems with hydraulic elevators
include underground electrolytic destruction of the cylinder and bulkhead, pipe failures, and control failures. Single bulkhead cylinders, typically built prior to a 1972 ASME A17.1 Elevator
Safety
Code change requiring a second dished bulkhead, were subject to possible catastrophic failure. The code previously
permitted only single-bottom hydrau1tc cylinders. In the event of a cylinder breach, the fluid loss results in uncontrolled
down
movement of the elevator. This creates two significant hazards.
being subject
to an Impact at the bottom
when the elevator stops suddenly and being in the entrance for
a potential shear if the rider Is partly in the
elevator. Because it is impossible
to verify the system at all times, the code requires periodic
testing of the pressure capability. Another solution to
protect against a cylinder
blowout is to Install a plunger gripping device Two commercially
available are known by the marketing names “Life Jacket" and Hydro Brake· The plunger gripper
is a device which, in the event of an uncontrolled
downward acceleration nondestructively
grips the plunger
and stops the car A device known as an over speed or rupture valve is attached to
the hydraulic inlet/outlet of the cylinder
and Is adjusted
for a maximum now rate. If a pipe or hose were to break (rupture),
the flow rate of the rupture
valve
will surpass a set
limit and
mechanically stop
the outlet now of hydraulic
fluid. thus stopping the plunger
and the car in the down direction.
In addition
to the safety concerns for older hydraulic
elevators. there is risk of leaking hydraulic oil into the aquifer
and causing potential
environmental contamination.
This has led to the introduction of PVC liners (casings) around hydraulic cylinders which can be monitored for integrity.
In the past decade, recent innovations in Inverted
hydraulic jacks have eliminated the
costly
process of drilling the ground to install
a bore hole jack. This also eliminates the threat of corrosion
to the system and increases safety.
- Mine-shaft elevators
Safety testing of mine shaft elevator rails is routinely undertaken. The method involves
destructive testing of a segment of the cable. The ends of the segment
are frayed, then set in conical
zinc molds. Each end of the segment
is then secured in a large,
hydraulic stretching machine. The segment is then placed under increasing load to the point of failure. Data
about elasticity, load, and other factors is compiled and a report is
produced. The report is then analyzed to
determine whether or not the entire rail is safe to use.
Ø Uses
Passenger service
A passenger elevator
is designed to move people between
a building's floors.
Passenger elevators capacity
is related to the available
floor space. Generally, passenger elevators
are available in capacities from 500 to 2,700 kg (1,000-6,000 lb) In 230 kg (500 lb) increments. Generally, passenger elevators
in buildings of eight floors or fewer are hydraulic or elevators, which can reach speeds
up to 1 m/s (200 ft./min) hydraulic and up
to 152 m/min (500 ft./min) electric in buildings up to ten floors,
electric and gearless
elevators are likely
to have speeds up to 3 m/s
(500 ft./min), and above ten floors speeds range 3
to 10 m/s (500-2,000 ft./min).
Sometimes passenger elevators
are used as a city transport along with funiculars. For example, there is a 3-station underground public elevator in Yalta, Ukraine, which takes passengers from the top of a hill above the Black Sea on which hotels are perched, to a tunnel located
on the beach below. At Casco Viejo station in
the Bilbao Metro,
the elevator that provides access to the station from a hilltop neighborhood doubles as city transportation: the station's
ticket barriers are set up m
such a
way that passengers
can pay to reach the elevator
from
the entrance in the tower city, or vice
versa. See also the Elevators for urban transport
section.
Passenger elevators
may be specialized for the service they perform, including: hospital emergency
(code blue), front and rear entrances, a television in high-rise buildings, double-decker, and other uses. Cars may be ornate in their interior appearance, may have audio visual advertising, and may be provided with specialized recorded voice announcements. Elevators may also have loudspeakers in them to play calm, easy listening music. Such music is
often referred to as elevator music.
An express elevator
does not serve all floors. For example, it moves between the ground floor and a sky
lobby, or it moves from the ground floor or a sky lobby
to a range of floors,
skipping floors
in between. These are especially popular in eastern Asia.
Capacity
Residential elevators may be small enough to only accommodate one person while some arc large
enough for more than a dozen. Wheelchair, or platform elevators. a specialized type of
elevator designed to move a wheelchair 3.7 m (12 ft.) or loss, can often accommodate just one-person m a
wheelchair at a time with a load of 340 kg (750 lb).
Freight elevators
A freight elevator, or goods lift, is an elevator designed to carry goods, rather than passengers. Freight elevators
are
generally required to display
a written notice In the car that the use by passengers is prohibited (though not necessarily illegal), though certain freight elevators allow dual use through the use of an inconspicuous riser. In order for an elevator to be legal to carry passengers in some jurisdictions it must have a solid inner door. Freight elevators are typically
larger and capable of carrying
heavier loads than a passenger elevator, generally from 2,300 to 4,500 kg. Freight elevators
may have manually operated doors, and often have rugged interior finishes
lo prevent damage
while loading and unloading. Although hydraulic
freight elevators exist. electric elevators are more energy
efficient for the work of freight lifting.
Sidewalk elevators
A sidewalk elevator is a special type of
freight elevator. Sidewalk elevators are used to move materials between
a basement and a ground-level area, often the sidewalk just outside the building. They are controlled via an exterior switch and emerge from a· metal trap door at
ground
level. Sidewalk elevator cars feature a
uniquely shaped top that allows this door to open and close
automatically.
Stage lifts
Stage lift and orchestra lifts ore specialized elevators, typically powered by hydraulic,
that are
used to raise and lower entire sections
of a theater stage. For example, Radio city Music hall tum four such elevators: an orchestra lift that covers a large area of the stage, and three smaller lift near the rear of the stage. In this case, the orchestra
lift is powerful enough to raise an entire orchestra,
or an entire cast of performers (Including live elephants) up to stage level from below. There's a barrel on the background of the Image of the loft which can be used as
a scale to represent the size of the mechanism.
Vehicle elevators
Vehicular elevators are
used
within buildings or areas with limited space (in place of ramps), generally to
move into the parking garage
or manufacturer's storage.
Geared hydraulic chains (not unlike bicycle chains) generate
lift for the platform and there are no counterweights. To accommodate building
designs and improve
accessibility, the platform may rotate so that the drive
only has to drive forward. Most vehicle elevators have a weight capacity of 2 tons.
Rare examples of extra-heavy elevators for 20-ton lorries, and even for rail cars (like one that was
used at Dnipro Station of the Kiev Metro) also occur.
Boat lift
In some smaller canals,
boats and small ships can pass between
different levels of a canal with boat elevator rather than through a canal lock.
Aircraft elevators
For aircraft
On aircraft carriers, elevators carry aircraft between the flight deck
and the
hangar deck for operations or repairs. These elevators are designed for much greater
capacity than other elevators, up to 91,000 kg (200,000 lb) or
aircraft and equipment. Smaller elevators
lift munitions to the flight
deck
from magazines deep inside the ship.
Within aircraft
On some passenger double-deck aircraft such as the Boeing
747 or other wide body aircraft, elevators transport flight attendants
and food and beverage trolleys
from lower deck galleys to upper passenger carrying decks.
Limited use and limited application
The limited-use, limited-application (LU/LA) elevator is a special
purpose passenger elevator
used infrequently, and which is exempt from many commercial regulations and accommodations. For example, a LU/LA is primarily meant to be handicapped accessible, and there might only be room for a single wheelchair and a standing passenger.
Residential elevator
A residential elevator or home
lift Is often permitted to be of lower cost and complexity than full commercial
elevators. They may have unique design
characteristics suited for home furnishings, such as hinged wooden shaft-access doors rather than the typical metal sliding doors of
commercial elevators. Construction may be less robust than in commercial designs
with shorter maintenance periods,
but safety systems such as locks on shaft access doors, fall arrestors,
and emergency
phones
must still be present in the event of malfunction.
The American
Society of Mechanical
Engineers (ASME) has a specific section of Safety Code (ASME A17.1 Section 5.3) which addresses Residential Elevators.
This section allows for different
parameters to alleviate design complexity based on the limited use
of a residential
elevator by a specific user or
user
group. Section 5.3 of the ASME A17.1 Safety Code is
for Private Residence Elevators, which does not include
multi-family dwellings.
Some types of residential elevators do not use a traditional elevator shaft, machine room, and elevator hoist way. This allows an elevator
to be installed
where a traditional elevator
may not fit, and
simplifies installation The ASME board first approved machine-room-less systems in a revision of the ASME A17.1 in 2007. Machine-room-less elevators have been available
commercially since the mid-1990s, however
cost and overall size prevented
their adoption to
the residential elevator
market until around 2010.
Also, residential elevators are smaller
than commercial elevators. The smallest passenger
elevator is pneumatic,
and
it allows for only 1 person. The
smallest traction elevator allows for just 2 persons.
Dumbwaiter
Dumbwaiters are small freight elevators
that are intended to carry food, books or other small freight loads rather than passengers. They often connect kitchens to
rooms
on other floors. They usually do not have the same safety features found in passenger
elevators, like various
ropes for redundancy. They have a lower capacity, and they can be up to 1 meter (3 ft.)
tall. Control panels at
every
stop mimic those found in passenger elevators, allowing calling, door control and floor selection.
Paternoster
A special type of elevator is
the paternoster, a constantly moving
chain of boxes. A similar
concept called the man lift
or human lift
moves only a small platform, which the
rider
mounts while using a handhold seen in multi-story industrial plants.
Scissor Lift
The scissor lift is yet another type of lift. These
are usually mobile work platforms
that can be easily
moved to where they are needed, but can also be installed where space for counter-weights,
machine room and so forth is limited.
The mechanism
that makes them go up and down is like that
of a
scissor jack.
Rack-and-pinion elevator
Rack-and-pinion elevator are powered by a motor driving
a pinion gear. Because they can be installed on a building or
structure's exterior and there is no machine room or hoist way
required, they are the most used type of elevator for buildings under construction (to move materials
and tools up and
down)
Material handling belts and belt elevators
Material transport elevators generally consist of an inclined plane on which a conveyor belt runs. The conveyor often includes partitions to ensure that the material
moves forward. These
elevators are often used in industrial and agricultural applications. When such mechanisms (or spiral screws
or pneumatic transport) are used to elevate grain
for storage in large vertical
silos, the entire structure
is called a grain elevator. Belt
elevators are often used in docks
for loading loose materials
such as coal, iron ore and grain into the holds
of bulk carriers.
There have occasionally been belt lifts for humans;
these
typically have steps about every 2
m (6 ft. 6. 7 in) along
the length of the belt, which moves vertically,
so that the passenger can stand on one step .and hold on to the one above. These belts are sometimes used, for example, to carry the employees of parking garages,
but
are considered too dangerous
for public.
Ø Parts
of Elevator and Its Function
In this article, we will tell you about the various parts of elevators and its function. Elevators have been around for many years. Let's here toke a closer look at parts of elevators and its function.
Speed Governors
The speed
regulating system of elevators
is known as the speed governor. If
the elevator runs more than the speed limit, the speed governor controls the
speed. It
is usually attached to the
bottom of the car and is also known as governor rope.
Electric Motor
In case the lift faces any serious condition, Electric Motors helps in preventing it and provides a
smooth
functioning of lifts.
Elevator Rails
Sliding up and down in the elevators is possible
with the proper functioning of Elevator Rails.
Cabin
This is the main part of Elevator which is designed for the shipment of goods and services or the passage of
persons.
Elevator Shaft
Lift cabin moves in this space. Depending upon the type of elevator,
the
location of the shaft can be
varied.
Doors
As normal doors, elevator
doors are also meant for entry and exit.
Elevator door is of two types: Manual
doors and Automatic doors.
Manual doors:: These types of doors are opened with the help of a person who wants to enter the lift
Automatic
doors: Automatic doors are the type of doors which are
automatically opened as it
is powered
by
a door operator.
Drive unit
Everything
that works under electricity must have a motor attached for the functioning.
Drive
unit is the part which contains a
motor
that drives the
lift.
Buffers
The buffer is an apparatus
located at the bottom of elevator designed to protect people. Buffers
can
stop a descending car by accumulating or dissipating the kinetic energy of the car.
Safety device
This is a mechanical device attached to the elevator for safety reasons.
In case the lift travels downward with a maximum
spud or over the spud
limit, safety device can maintain a safety and secure
traveling.
Well, these were some of the
parts of elevators and its function.
Traveling is an elevator is just amazing. But the skills and knowledge of technician and the effective
maintenance of the elevators can bring up the travel
an extraordinary one.
Ø Current elevator manufacturers
- Acorn Stair1ifts
- Aichi small-elevator manufacturing corporation
- Anton Freissler invented and developed a number of paternoster and elevators
- Canton Elevator Incorporated
- Delaware Elevator Manufacturing
- Fujitec
- Stannah Lifts
- Sicher elevator
- Hitachi
- Hyundai Elevator
- Kone
- KLEEMANN
- LG Elevator
- Marshall Elevator
- MEI-Total Elevator Solutions
- Mitsubishi Electric
- Orona Group
- Otis Elevator Company
- Schindler Group
- Schumacher Elevator Company
- Sigma Elevator
- Johnson elevator
- GYG elevator
- Hanjin elevator
- Thys$enKrupp
- Toshiba
- FUJIHD
- Cibes Lift
- ulift
- Delta Elevator
- Liftech SA
Ø Home elevator manufacturers
- Domus lift
- PV elevators
- Lifting Italia
- Nova lifts
- Sele elevators
- Gruppo Millepiani
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