Passenger elevator is a device used for transporting persons, luggage and goods between different floors of multi-storied buildings. Of the various types of elevators available, commercial elevators are the powerful ones and find a wide range of applications in healthcare centers, shopping malls, multiplexes and small scale industries.
Elevator control systems are probably the only part of the elevator that has seen major improvements over the last century. It was not that long ago that every passenger elevator had an operator who controlled the elevator, starting and stopping the elevator manually, based on the requests of those riding the elevator and signals from those waiting for the elevator.
An efficient control system will enable the person waiting for an elevator to signal his destination before the elevator arrives at his floor. A computerized system determines the most efficient car for him to board. In our example, the first car to pass the 23rd floor may be stopping 6 times between the 23rd and 40th floors.
However, a car that will arrive only a few seconds later has a passenger who wants to alight from the elevator on the 23rd floor anyway, and will only make 2 stops before it reaches the 40th floor. By causing the potential rider to wait a few seconds before boarding an elevator, not only can a significant amount of energy be saved, but the rider will actually reach his destination faster than he would have if he had boarded the first elevator ascending past the 23rd floor.
This system was replaced by a set of buttons inside the passenger elevator , with a single button for each floor, and two buttons used for calling the elevator - an up button and a down button. This method enables the elevator to determine whether or not the direction in which the elevator is travelling is relevant to the person waiting to board.
With the advent of very tall buildings, elevators were assigned specific ranges of floors on which to operate. This allows an express elevator to 'jump' 50 floors or more before making frequent stops. This too improved efficiency.
Passenger elevator are of hydraulic or electrical types and are available in varying lifting capacities ranging from 1,000 lb to 6,000 lb. Passenger elevator that travel 8 floors or less can reach speeds upto 200 ft/min. In the case of electric elevator it is 500 ft/min. Acceciblity equipments that travel above ten floors have speeds ranging from 500 ft/min to 2000ft/min. Passenger elevator are commonly used in buildings having 2-8 floors.
However, drawbacks remain. If, for example, a person on the 23rd floor of a building is waiting for a passenger elevator to take him to the 40th floor, he has no way of making this known to the elevator other that by pushing the up button. The next ascending elevator will stop regardless of the number of stops it must make between the 23rd and 40th floors.