When was the automatic door invented? The first known automatic door was described nearly 2,000 years ago by Hero of Alexandria. It was designed to make the doors of a small temple magically open when a fire was lit on an altar. Electronic automatic doors were invented so waiters could more easily carry food through. And the pneumatic automatic door closer that we see on many doors today was invented to stop a church door from slamming.
Doors that close automatically are relatively simple to build and they have existed since ancient times. They usually involve a rope and a weight tied to the door. When a person opens the door, the energy they apply pulls the weight up. The weight now has gravitational potential energy and when you release the door, the weight is lowered down, closing the door. This is very simple to do. A door that opens automatically is much more complicated.
The world’s first automatic door was invented by Hero of Alexandria. He lived in Alexandria in probably the 1st century AD and he was one of the greatest inventors who ever lived. He described an extraordinary collection of machines, including an aeolipile powered by steam, a coin-operated holy-water dispenser, pumps, automata, and even a wind-powered machine. He also invented the first automatic door with a brilliant design. They were designed for temple doors in Alexandria. There is no definite evidence that the doors were ever used on the real temple, but they would have worked. The design worked on atmospheric pressure. Inside the temple was a hollow, sealed altar containing air that was connected by a pipe to a partly filled water container underneath. When the priest goes into the temple in the morning, he lights a fire on the altar. The fire slowly heats the trapped air inside the altar. As the air heats it expands and the pressure increases. The increased pressure pushes water out of the container through a pipe and into a hanging bucket. As the bucket fills with water, it gets heavier and finally drops. The bucket is attached by ropes and pivots to the temple doors and as it drops, it swings the doors open. If timed properly, the doors will open just as people are coming to the temple to worship. Then, here is the clever bit, when the fire is extinguished, the pressure drops and the water is sucked out of the bucket. The bucket becomes lighter and a counterweight closes the doors again. Whether or not it was actually used, it is an amazing design and an early example of a primitive heat engine.
It was almost two thousand years before automatic doors became common. Two engineers, Horace H Raymond and Sheldon S Roby invented an optical device to open a set of automatic doors. They installed it at Wilcox’s Pier Restaurant so that the waiters could get from the kitchen to the dining room without having to open the door with their feet or backs. The optical device was a photoelectric eye that detected when a light stream was broken and initiated the door open and closing. Then, in 1954, Dee Horton and Lew Hewitt developed an automatic sliding door activated by a pressure mat. They later founded Horton Automatics and commercially marketed automatic sliding doors in 1960. Both of these inventions increased the take up of automatic doors in many American buildings. Then, in the 1970s, motion sensors were invented and the number of automatic doors rapidly increased.
And, lastly, the pneumatic automatic door closer was invented by Lewis C. Norton. In 1877, Norton was working as a foreman at Trinity Church in Boston when the rector complained about a storm door that kept slamming during his sermons. Norton tried putting rubber around the door, but that only changed the bang into a thump. One day, while trying to solve the problem, Norton went to throw his tools into a small closet and tried to slam the door. The air trapped inside the closet stopped the door from closing quickly, and Norton realized that he could use the same principle to control the church door. He adapted a small hand-operated pump to create a pneumatic device that resisted the spring pulling the door closed, allowing it to close slowly and quietly instead of slamming. He later combined the spring and pneumatic mechanism into one device and patented his “door check and spring” in 1880. Norton continued improving door closers for decades, and his inventions eventually developed into the modern pneumatic door closers we still use today. And this is what I learned today.
Sources
https://en.wikipedia.org/wiki/Automatic_door
https://en.wikipedia.org/wiki/Hero_of_Alexandria
https://en.wikipedia.org/wiki/Stanley_Black_&_Decker
https://www.chinaautomaticdoor.com/info/the-history-of-automatic-doors-94152948.html
https://www.sopl.us/blog/the-history-of-door-closers
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