Revolving doors are generally made of four panels which are joined to a central shaft which rotates in a glass enclosure. Weather strips on the side of each panel creates a seal between the panel and the cylinder.
The first revolving door, the ‘Door without draft of air’ was patented by H. Bockhacker of Berlin in 1881 but it did not gain much popularity. Later, Theophilus Van Kannel, of Philadelphia applied for a patent for his ‘Storm-Door Structure’ in 1888. It is said that Kannel was inspired to invent the revolving door since he was against chivalry and did not like to hold the door for a woman. Interesting, isn’t it?!
Kannel claimed that the advantage a revolving door had over a swinging door was that it prevented the entry of wind, snow, rain or dust. It rotated only in one direction so the possibility of collision was greatly reduced.
Apart from controlling the flow of people traffic, the revolving door soon became the basis for research on conservation of energy. The door helps in reducing energy losses since it prevents warm air from escaping. One of the earliest research was carried out in 1936 by A. M. Simpson, who worked for Kannel’s company.
Another research conducted by students of MIT in 2006 found that revolving doors could save significant amounts of energy. They even urged other students to use the revolving doors by putting up signs around the campus. Their strategy worked resulting in more students using the door.
The world’s first wooden revolving door was installed at Rector’s, a restaurant on Times Square in Manhattan. In 2007, Kannel was inducted into the National Inventors Hall of Fame for his invention.