elevator
An elevator or lift (in british English) is a vertical transport vehicle that efficiently moves people or goods between floors of a building, They are generally powered by electric motors that either drive traction cables or counterweight systems , or pump hydraulic fluid to raise a cylindrical piston
Design
lifts began as simple rope or chain hoists. A lift is essentially a platform that is either pulled or pushed up by a mechanical means. A modern day lift consists of a cab (also called a "cage" or "car") mounted on a platform within an enclosed space called a shaft or sometimes a "hoistway". In the past, lift drive mechanisms were powered by steam and water hydraulic pistons . In a "traction" lift, cars are pulled up by means of rolling steel ropes over a deeply grooved pulley, commonly called a sheave in the industry. The weight of the car is balanced with a counterweight. Sometimes two lifts always move synchronously in opposite directions, and they are each other's counterweight. The friction between the ropes and the pulley furnishes the traction which gives this type of lift its name.
Hydraulic lifts use the principles of hydraulics (in the sense of hydraulic power) to pressurize an above ground or in-ground piston to raise and lower the car. Roped hydraulics use a combination of both ropes and hydraulic power to raise and lower cars. Recent innovations include permanent earth magnet motors, machine room-less rail mounted gearless machines, and microprocessor controls.
which technology is used in new installations depends on a variety of factors. Hydraulic lifts are cheaper, but installing cylinders greater than a certain length becomes impractical for very high lift hoistways. For buildings of much over seven storys, traction lifts must be employed instead. Hydraulic lifts are usually slower than traction lifts.
Lifts are a candidate for mass customization. There are economies to be made from mass production of the components, but each building comes with its own requirements like different number of floors, dimensions of the well and usage patterns.
Passenger service
A passenger lift 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 1,000 to 5,000 pounds (455 to 2,270 kilograms) in 500-pound (230-kilogram) increments. Generally passenger elevators in buildings eight floors or less are hydraulic or electric, which can reach speeds up to 200 ft/min (1 m/s)hydraulic and up to 500 ft/min electric. In buildings up to ten floors, electric & gearless elevators are likely to have speeds up to 500 ft/min (2.5 m/s), and above ten floors speeds begin at 500 ft/min (2.5 m/s) up to 2000 ft/min (10 m/s).
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.
Types of passenger elevators
Passenger elevators may be specialized for the service they perform, including: Hospital emergency, front and rear entrances, 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 instructions.
All elevators are required to have communication connection to an outside 24-hour emergency service, automatic recall capability in a fire emergency, and special access for fire fighters' use in a fire. Elevators should not be used by the public if there is a fire in or around the building. and numerous building codes requires signs to this effect be posted near the elevator. However, emergency evacuation in some countries do allow the use of special 'fire elevators'.
Capacity
Residential elevators may be small enough to only accommodate one person while some are large enough for more than a dozen. Wheelchair or platform lifts, a specialized type of elevator designed to move a wheelchair 6 ft(1.8 m) or less, often can accommodate just one person in a wheelchair at a time with a load of 1000 lb (455 kg).
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 certain freight elevators allow dual.
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 to prevent damage while loading and unloading. Although hydraulic freight elevators exist, electric elevators are more energy efficient for the work of freight lifting.
Vehicle elevators
Vehicular elevators are used within buildings with limited space to move cars into the parking garage. 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 driver always drives forward instead of in reverse.
Boat elevators
In some smaller canals, boats and small ships can pass between different levels of a canal with a boat lift rather than through a canal lock.
Aircraft elevators
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 ever built, up to 200,000 pounds (20 tonnes) of aircraft and equipment. Smaller elevators lift munitions to the flight deck from magazines deep inside the ship.
General controls
A typical modern passenger elevator will have:
Space to stand in, guardrails, seating cushion (luxury)
Electric fans or air conditioning units to enhance circulation and comfort.
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). In the United States and other countries, call button text and icons are raised to allow blind users to operate the elevator; many have Braille text besides.
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. Objects in the path of the moving doors will either be detected by sensors or physically activate a switch that reopens the doors. Otherwise, the doors will close after a preset time.
A stop switch (not allowed under British regulations) to halt 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 trigger an alarm. Unless local codes require otherwise, this will most likely be a key switch.An alarm button or switch, which passengers can use to signal that they have been trapped in the elevator.
Some elevators may have one or more of the following:
An elevator telephone, which can be used (in addition to the alarm) by a trapped passenger to call for help. 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.. A second or more set of doors that can serve different floor plans. 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.
Security camera
Plain walls or mirrored walls giving the illusion of larger area 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 to enable or disable the elevator.
An inspector's 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.
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