The nut is usually rotatably driven to achieve vertical movement. The details of different transportations systems are explained further.
Elevators are mostly used to transport people, called passenger elevators. They can also be used to transport materials in which case they are called freight elevators. Whether the elevator is for people or for material, there are basically two types of systems.
One is overhead suspended elevator and another is hydraulic elevator. Suspended elevator uses steel cables and electric motors. These usually travel fast and are therefore used for tall buildings. Hydraulic elevator is operated by a hydraulic piston which is situated in a chamber below the elevator cab. The piston moves in a rotatory motion about its pivot which in turn makes the cab traverse vertically.
Elevator cabs move along vertical guide rails. For suspended elevators, an electric motor runs which lowers and raises the cab with the help of wired ropes. These ropes are designed to suit the capacity of the cab. It also has a flexible electric cable connected to it in order to provide lightning and also to facilitate button and door signals to be transmitted.
The construction of both kinds of elevators requires considerable effort below the point of lowest entry to cab. If the elevator serves the lowest building level, then it requires considerable depth of excavation and construction below the basement of the building. Also, for every cab, corridors need to be planned in the building accordingly. For material carrying elevators, the corridors should be relatively big depending upon the usage.
The elevator shaft must be vertically aligned to maintain constant pressure in all floors. The size and dimensions vary depending upon size of the cab and number of elevators. For small or single cab, the area may be only of the cab but for larger cabs and for multiple elevators, the lower floors need to have a larger base. The plan for operating single or multiple elevator cabs can be seen in the figure below:
Escalators are moving stairs which serve the same purpose as an elevator. However, escalators provide a more uninterrupted service compared to elevator due to the waiting time for elevators.
Escalator works on the principle of conveyer belts. The difference is that a pair of rotating chain loops pulls a series of stairs in a cycle instead of a flat surface. The most important part is to make sure the steps are always in level which the escalator moves. However, at the top and bottom, the steps become in one level making it easier to get on and off. Escalator also has hand rails which move along with the escalator. The hand rail is controlled by an electric motor which runs a rubber belt around a series of wheels. It is configured in a way that the hand rail moves with the same speed as the elevator.
When not operating, escalators serve as stationery stairs; therefore their slopes are subject to same limits that exist for stairs. Thus the plan space required for an escalator begins with that required to achieve a stair for total height.