The next time you step between the panels of a revolving door, take a closer look. Most revolving doors are composed of three or four individual panels; those used to accommodate more than one person have only two panels. Regardless of the number of panels, all fan out from a central shaft that rotates within a glass-enclosed cylinder. Weather stripping on the side of each panel creates a seal between the panel and the cylinder. Curved walls allow a tighter fit. A revolving door's movement is powered either by someone pushing one of the door panels or by a motor that automatically rotates the doors [source: Made How].
This design has remained the same largely from its invention. The first patent in the world for a revolving door went to German inventor H. Bockhacker in 1881, but the idea didn't catch on.
In 1888, Pennsylvania resident Theophilus Van Kannel received the first U.S. patent for a three-way storm door with weather stripping to ensure an energy-efficient fit with the doorframe. He set up his own company, the Van Kannel Revolving Door Co., to manufacture his product. In 1907, Van Kannel sold it to International Steel (known today as the International Revolving Door Co.)
Although not much is known about Van Kannel's life, there's an interesting rumor concerning the inspiration behind his invention: He disliked the chivalrous act of holding open doors so ladies could pass through them. Thus, he spent most of his adult life focused on the invention, improvement and installation of revolving doors. He also never married.
Van Kannel was recognized for his invention both during his lifetime and posthumously. In 1889, he received Philadelphia's John Scott Medal for his invention's usefulness to society. In 2007, he was inducted into the National Inventors Hall of Fame [source: National Inventors Hall of Fame].
The revolving door is not Van Kannel's only claim to fame. He also invented the Witching Waves ride at Coney Island. The ride, which was installed in 1907, featured two-person seats that moved along an undulating metal floor [sources: National Inventors Hall of Fame, Stanton].
Van Kannel died in 1919 at age 78, but his revolving doors live on. Today, the doors have been paired with metal- and chemical-detection technology, and have become an important security feature in airports and detention centers. Some revolving doors even feature facial-recognition surveillance systems [source: Made How].