As the industrial revolution expanded, the new factory buildings started to be built with several floors. A method was needed to get materials from floor to floor. Construction workers built crude hoists using manual winches, animal power or steam power to move both materials and men. Hoists were also used in mines at even earlier times.
The early elevators had a serious flaw: When the hoisting rope broke, the elevator fell. If you were on the third floor of a building and the rope broke, you would fall to about the second floor in the time it took your mind to react to the emergency, and about the time you pulled on the emergency brake lever, if there was one, you had already hit the ground. Even if there was a brake, it might not be able to halt a heavily loaded elevator.
In 1853 Elisha Otis invented the first automatic safely device. If the hoisting rope broke, a spring pushed latches into a toothed rack built into the elevator guide rails, stopping the elevator instantly without any action by anyone in the elevator. This automatic safety device, modeled in the photo on the right, made the elevator a safe way to move materials and people vertically in a building, and enabled the elevator business to become commercially viable.
This "winding drum" type drive is an example of the earliest form of elevator hoisting system. The drum was usually located in the basement of a building and driven by a small steam engine.
This was a rather slow system and to insure long hoisting rope life and minimize rope breakage, only one layer of rope was carried on the drum. This severely limited the height of the lift.
Steel frame building construction quickly exceeded the height that a "winding drum" type elevator could service.
The "hydraulic" elevator increased the speed and height of elevators. These are driven by a hydraulic piston and cylinder sunk into the floor of the building. Fluid pressure moves the piston against the floor of the elevator car, raising the car to the required height. However, the cylinder must be the same height as the building, limiting its use to relatively low structures such as apartment buildings or small office buildings. The first four elevators of this type were installed in the Boreel Building in New York in 1878.
The early models used the city water pressure for power. This meant that the control system was just a water valve, much simpler and more dependable than trying to control a steam engine in the basement. Current models use hydraulic fluid rather than water.
But again steel frame building construction quickly exceeded the height that a "hydraulic" type elevator could service. Something else was needed to service tall buildings.
The traction drive depends on the friction, or traction, between the hoisting ropes and the drum. The hoisting ropes are wound over the drum (possibly several turns are made) and down to the counter weight, which compensates for the weight of the empty elevator car and vastly reduces the power needed by the hoisting motor. Almost any length of rope (steel cable) can connect the car and counterweight. Above 100 stories the weight of the ropes starts to be an important factor, but this is not a limit yet.
The invention of the "traction" type drive took away almost all limits on the height of buildings, enabling the construction of "skyscrapers". At present, nearly all elevators six stories or less are hydraulic and those above six stories are traction drive.
The elevator operator
Today's elevators are controlled by pushing buttons on a panel in the elevator car - an operation so straightforward that whether you are a child or an adult, it is done so easily that you don't even think about it. But it wasn't always so easy. In the days before electronics, each elevator car required an operator, whose job was to open and close the doors, control the direction and speed of movement, take requests from elevator passengers, and announce what might be found at each stop. In short, a kind of vertical bus driver. In department stores, the operator was a valuable tool for good public relations, and in office buildings, operators provided a familiar face and a friendly word (hopefully) to workers as they arrived or departed.
Many of the elevators manufactured between WW I and WW II were elaborately decorated or finished in fine woods. Others incorporated fine metalwork and artistic art deco or art nouveau fixtures. An elegant elevator was considered an asset in providing an image of success, quality and financial strength. In the elevator depicted here (which at one time was located in a Miami movie palace and now graces the Hotel Place St. Michel in Coral Gables, FL), the floor is done in wood parquet, fine wood panels line the floor and ceiling, and ornamentation is provided by grillwork and other touches. Gilding of grillwork and electrical fixtures was not uncommon. Note also the tile work surrounding the elevator door on the ground floor.There are only a few hand-controlled passenger elevators still operating in the U.S., so the elevator shown here, manufactured by the Otis Elevator Company, is a piece of living history.
The controls are more utilitarian: A hand operated controller for speed and direction, an annunciator panel to inform the operator that a would-be passenger has pushed a call button, and a floor control that must be depressed by the operator in order to allow the doors to open--a simple, but effective, safety device. Some employers would have required the elevator operator to polish the brasswork when not otherwise engaged. The controller handle was pushed forward to cause the elevator to descend, and pulled rearward to rise. It sounds simple, but a certain amount of skill and finesse was required to do the job properly.It was the responsibility of the operator to align the floor of the elevator with the level of the floor at which a stop was made. A skilled operator could do this on-the-fly in a smooth operation. Less skilled operators subjected their passengers to time-consuming and nerve-wracking up and down motions until they got it right.
Elevator operators were still a common site at the beginning of the 1950s, but by the beginning of the following decade, they had largely vanished from the American scene, displaced by the increasing use of electronics, ever-cheaper automation and the ubiquitous pushbuttons.
| This page last updated: May 10, 2003
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