April 12, 2013 | 1
2013 marks 160 years since Elisha Graves Otis sold his first elevator, designed specifically for safety. Sales languished, though, until he attended the 1854 world’s fair in New York City and, at the Crystal Palace, demonstrated the innovation that made elevators stop, instead of falling, if their cables snapped.
Scientific American, of course, had an early interest in Otis and on November 25, 1854, published a detailed explanation of how his elevator guarded against free falls, complete with the diagram at the right. (For clarity, we have improved the legibility of the lettering.)
The article notes that when power is applied to the lifting rope (K), the rope pulls on a vertical rod (I), which in turn pulls on right-angled levers (H), thereby pulling two pawls (G) away from the racks (B) secured to the inner sides of the vertical posts (A). This system prevents the pawls from “bearing against the racks” during the upward movement of the frame (F) and platform (E), “and much friction is obviated thereby.” When the pull on the rope stops, the pawls automatically catch into the racks again. By design, the pawls are also kept free from the racks during the elevator’s normal downward passage.
“If the rope should break, or be loosened from the driving shaft, or disconnected from the motive power accidentally,” the story reports, “the platform will be sustained, and no injury or accident can possibly occur, as the [platform] is prevented from falling.”
Otis died in 1861, but his sons carried on his business. In 1886 we gave readers an update on the company’s technology and featured four gorgeous engravings. The captions here are excerpted from the originals.
Figure 1 shows the Otis passenger car with safety frame. The framework is constructed entirely of wrought iron; the lifting cables pass through it and are connected independently to the gravity wedge safety apparatus under the car, as shown. The value of the car shown is one thousand dollars.
Figure 2: Recently, Messrs. Otis have added the rubber buffer attachment, which is designed to relieve the car from shock or jar when starting or stopping, and to insure smoothness of motion in running at high speed. Several sizes of these engines are made.
Figure 3: The demand for a hydraulic hoist, in connection with steel manufacture, has induced Messrs. Otis to bring out their standard hydraulic freight elevator. This form of machine is intended for any duty, and to be operated under water pressure of from thirty to five hundred pounds. Two or more lifting cables are employed.
Figure 4: The Otis hydraulic machine, with direct pumping system, adapted to passenger and freight service, is specially designed for any building where it is not desirable to place a tank on the roof or the attic. Its operation is to pump under pressure directly on the piston. The water from the cylinder is discharged into the tank, and is used over again. Credit: Scientific American (all images)