ELEVATOR, a moving platform or cage in a building, for carrying passen gers or freight up and down.
Vitruvius, an architect of Rome about 26 B. C., describes in his writings an ap paratus built by Archimedes in the year 236 B. C. for lifting very heavy weights.
vator consisted of a cast-iron screw ex tending the total height of the building. The car was built around the screw, the rotation of which caused the car to move either up or down.
The first elevator to be operated suc cessfully by direct electric power, was designed and installed by the Otis Bro thers' Company in the Demarest Build ing, New York City, during the year 1889.
The modern electric high-speed gear less traction elevator was developed by the Otis Elevator Company, in 1904, the first installation of this type being in the New York Edison Company's Build ing, New York.
Elevators may be divided into five general classes: electric, hydraulic, steam, belt, and hand power, to which may be added the escalator or moving stairway.
Electric elevators, constituting about 90 per cent. of the installations of the pres ent time, are of two types, namely, those with winding drums and those with traction sheaves. The former type are designed with drums spirally grooved on which the cables wind and unwind in raising and lowering the elevator. Ele vators of the traction type are provided with straight grooved sheaves over which the cables pass, the friction be-. tween the sheave and the cables being utilized for raising and lowering the elevator. Figure 1 shows in diagram the usual arrangement of car, counter balance cables, etc., for an electric drum machine, while Figure 2 shows a similar arrangement for the traction type electric elevator. The worm-geared drum machine was almost universally used until the advent of the high-speed gearless traction machine which was designed to eliminate the excessive drum sizes required for tall buildings. The worm-geared traction machine has now been developed to cover the field of the worm-geared drum type machine. The elevator machinery may be located either at the base of the hatchway or over the top of the hatchway, the latter location being preferable as it simpli fies the arrangement.
There are three principal types of hy draulic elevators: the vertical, the hori zontal and the plunger type. Both the vertical and the horizontal types consist of a cylinder with piston rods connected to traveling sheaves, around which pass the cables which are attached to the car. By introducing water into the cylinder under pressure, the piston is caused to move and the car raised. To lower the car, the water is allowed to discharge from the cylinder, the weight of the car being sufficient to overcome the friction of the water through the valves, pipes, etc.
The plunger elevator consists of a tube sunk in the ground a distance equal to the rise of the elevator and a plunger attached to the bottom of the car work ing in this tube through a stuffing box.
Movement of the car is accomplished by water under pressure entering the cylin der, causing the plunger and the car to rise. To lower the car the water is allowed to discharge from the cylinder.
Except in special cases, very few hydraulic elevators are being installed at the present time, the cost of installa tion and also the cost of operation being much higher than for the electric type cf elevator.
The steam type of elevator consists of a steam engine as the motive power, geared to a winding drum around which the cables to the car pass. This type of elevator is practically obsolete at the present time.
The belt elevator is usually driven from a line shaft and is only used for slow speeds.
The hand power elevator is used only when the service is infrequent and the expense of installing a power-driven _elevator is not warranted. It is oper ated by pulling an endless rope over a driving sheave which is geared to the winding machine.
Safety features of elevator.—With the exception of the plunger type of eleva tor, practically all elevators are provided with what is known as a Safety Device, designed to grip the guide rails and stop the car if for any reason the speed of the elevator becomes excessive or if, due to the breaking of the lifting cables, the car starts to fall. Additional safeties are provided to automatically stop the car at the upper and lower terminal landings in case the operator neglects to do so, and if the car runs by these landings, to cut off the supply of cur rent, apply the brake, and bring the car to rest.
In connection with high-speed traction elevators, the gearless type of which is used for passenger service in the modern office buildings of our large cities, it is usual to provide oil-cushion buffers un der the car and under the counter weight. If, due to accident, the car runs past the upper or lower landings, these buffers are compressed, bringing the car gradually to rest and at the same time reducing the traction between the lift ing cables and the driving sheave. This is a very important safety feature as it prevents any further travel of the car or the counter-weight.
Taking the borough of Manhattan in the city of New York as an example, more than double the number of pas sengers are carried vertically in elevators than are carried by the surface, subway, and elevated lines combined, while the percentage of accidents to passengers traveling in elevators is very much less. This is due to the exceptional safety features provided in connection with passenger elevators.
ELF, a little sprite supposed to inhabit wild and desolate places, and to exer cise a mysterious power over man; a fairy, a goblin.