The Invention and Development of Elevator II

Date:2016-10-14

Improved versions of the steam-driven elevator appeared in the next three decades, but no significant advance took place until the introduction of the electric motor for elevator operation in the mid-1880s and the first commercial installation of an electric passenger elevator in 1889. This installation, in the Demarest Building in New York City, utilized an electric motor to drive a winding drum in the building’s basement.

The introduction of electricity led to two further advances. First, in 1894, push-button controls were introduced, and second, in 1895, a hoisting apparatus was demonstrated in England that applied the power to the sheave (pulley) at the top of the shaft, with the weights of the car and counterweight sufficed to guarantee traction.

By removing the limitations imposed by the winding drum, the traction-drive mechanism made possible taller shafts and greater speeds. In 1904, a “gearless” feature was added by attaching the drive sheave directly to the armature of the electric motor, making speed virtually unlimited.

With the safety, speed, and height problems overcome, attention was turned to convenience and economy. In 1915, so-called automatic leveling was introduced in the form of automatic controls at each floor that took over when the operator shut off his manual control within a certain distance from the floor level and guided the car to a precisely positioned stop.

Besides, power control of doors was added. And with increased building heights, elevator speeds increased to 1,200 feet (365 metres) per minute in such express installations as those for the upper levels of the Empire State Building (1931) and reached 1,800 feet (549 metres) per minute in the John Hancock Center, Chicago, in 1970.

Automatic operation, widely popular in hospitals and apartment buildings because of its economy, was improved by the introduction of collective operation, by which an elevator or group of elevators answered calls in sequence from top to bottom or vice versa. The basic safety feature of all elevator installations was the hoistway door interlock that required the outer (shaft) door to be closed and locked before the car could move. By 1950, automatic group-supervisory systems were in service, eliminating the need for elevator operators and starters. This article from fujihd.net.

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