Revolving door
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- For the political advertisement, see Revolving Door (television advertisement).
A revolving door is a type of door that, as its name suggests, revolves in its frame. A revolving door, however, is set on a rotating shaft and has unlimited rotation.
Around the shaft are several doors (called "wings" or "leaves) that are bolted to it and incapable of independent movement. The usual number of doors on a revolving door is three or four. Large revolving doors that accommodate strollers and luggage racks only have 2 wings.
The doors may be powered via the central shaft or if a small shaft is desirable, the perimeter may be driven instead. Powered revolving doors have safety sensors but fatal accidents have occurred[1].
Manual revolving doors have pushbars on them. When the pushbar of the door facing the user is pushed, the entire assembly rotates. The doors are transparent to allow users on either side of the door to see and anticipate each other to avoid being surprised by sudden operation. Manual doors typically have speed governors to prevent patrons from spinning the door too fast.
There are a pair of curved partial walls around the circumference of the revolving door with only openings sized to match an individual section of the revolving door. Thus, the revolving door prevents a direct path between the interior and exterior. In a sense, such a door is always closed, so wind and drafts cannot blow directly into the building. Revolving doors are favored because they can be used as a partial airlock to minimize a building's heating and air conditioning losses. Some versions permit the individual doors of the assembly to be unlocked from the central shaft to permit free flowing traffic in both directions.
In right hand drive countries, revolving doors typically revolve counterclockwise, allowing people to enter and exit only on the right side of the door. In left hand drive countries, revolving doors should revolve clockwise but not always[2].
Revolving doors can also be used as security devices to restrict entry to a single person at a time if the spacing between the doors is small enough. This is in contrast to a normal door which allows a second person to easily "tailgate" an authorized person.
Sometimes a revolving door is designed for one-way traffic. An example is the now-common usage in airports to prevent a person from bypassing airport security checkpoints by entering the exit. Such doors are designed with a brake that is activated by a sensor should someone enter from the incorrect side. The door also revolves backwards to permit the person to exit, while also notifying security of the attempt. One-way doors are also often used in subways and other rapid transit facilities to prevent people from avoiding a fare. These doors usually work mechanically with the door panels constructed of horizontal bars which pass through a bar "wall", allowing the door to pass through but not people.
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[edit] History
H. Bockhacker of Berlin was granted German patent DE18349 on December 22, 1881 for "Thür ohne Luftzug" or "Door without draft of air".
Theophilus Van Kannel, of Philadelphia, was granted US patent 387,571 on August 7, 1888 for a "Storm-Door Structure". The patent drawings filed show a three-partition revolving door. The patent describes it as having "three radiating and equidistant wings . . . provided with weather-strips or equivalent means to insure a snug fit". The door "possesses numerous advantages over a hinged-door structure . . .it is perfectly noiseless . . . effectually prevents the entrance of wind, snow, rain or dust . . ." "Moreover, the door cannot be blown open by the wind . . . there is no possibility of collision, and yet persons can pass both in and out at the same time." The patent further lists, "the excluding of noises of the street" as another advantage of the revolving door. It goes on to describe how a partition can be hinged so as to open to allow the passage of long objects through the revolving door. The patent itself does not use the term "revolving door".
"In 1889, the Franklin Institute of Philadelphia (the original home of the revolving door) awarded the "John Scott Legacy Medal" to Van Kannel for his contribution to society."[3]. "In 1899, the world’s first revolving door was installed at Rector’s, a restaurant on Times Square in Manhattan, located on Broadway between West 43rd and 44th Streets."[4]
[edit] Poor fire exit
In 1942, the Cocoanut Grove, a popular nightclub in Boston, MA went up in flames killing 492 people. Named after the nightclub, it became known as the Cocoanut Grove fire. One of the main reasons cited for the large number of casualties was the single revolving door located at the entrance. As the mob of panicking patrons attempted to use the door as an escape it soon became jammed, trapping countless people between the door and the crowd pushing towards it. As a result, many people died from smoke inhalation, not being able to escape the burning nightclub. In 1943 it became Massachusetts state law to either flank a revolving door with an outward swinging hinged door or make the revolving door collapsible (so it becomes a double partition (at 180°) allowing people to pass on either side.) Most (if not all) revolving doors in the US are now flanked by at least one hinged door either by common practice or required by law.
[edit] Metaphorical use
Metaphorically, a revolving door is an instance of the easy movement of individuals from one position or situation to another, and back again. For example, from government-related jobs to lobbying jobs and vice versa, resulting in a conflict of interest for those chosen to represent the public and/or special privileges and benefits to former government officials and personnel. A similar metaphor in the Japanese language is Amakudari, but it refers only to former government employees joining companies they were once supervising. This is also used when describing early release of criminals who often end up back in prison after a short time.
[edit] References
- Alan Beadmore, The Revolving Door since 1881: Architecture in Detail, 2000, ISBN 90-901374-3-2
- Harvey E. Van Kannel and Joanne Fox Marshall, T. Van Kannel, the inventor : his autobiography and journal, 1988, Library of Congress control number 88091258
