Door Closer

Modern manual door closer
A door closer is a mechanical device that closes a door, in general after someone opens it, or after it was automatically opened.

There are three styles of door-closer: surface-mounted, concealed in frame, and concealed in floor.

Surface mounted door closers come in four variations: Slide-track arm, regular arm surface mounted , parallel arm surface mounted, and top jamb mounted. Overhead door closers, such as those made by Norton, Dorma, Yale and Geze, are typically surface mounted, though most manufacturers offer concealed models too, such as the Norton 7900 series overhead concealed, or the Rixson 27 series concealed in floor closer. These closers mount inside a pocket in the door frame or are mounted in the floor directly under the pivot point and are completely concealed.

Manual door closer

A manual door closer stores the energy used in the opening of the door in a compression or torsion spring and releases it to close the door. Some closers allow for adjustment of the strength of the spring, making it easier or more difficult to push the door open. To limit the speed at which the door closes, most door closers use hydraulic (oil-filled) dampers, although spring mechanisms may also be used for damping. The speed at which the door closer closes the door may be adjustable by up to three adjustment valves. These valves often adjust the sweep speed and the latch speed of the door and some closers are optioned with a delayed action vlave. The latch speed is the speed that the door travels in the last third to 10 degrees as it closes and is often set fast so that the door can properly latch closed. The sweep speed is the speed which the door travels at along the first two thirds of its travel and is often set slower than the latch speed. For openings where a much longer close time is desired, you may opt for a delayed action closer. The delayed action valve slows the sweep speed dramatically for roughly the first half of the sweep range. Door closers which provide this two or three-stage action and close doors at a determined rate are called 'controlled' door closers.

Old type of manual door closer

Door closers are most commonly used on fire doors, which need to be closed in the case of fire to help prevent spread of the fire and smoke. Choosing a door closer can involve the consideration of a variety of criteria. In addition to the closer's performance in fire situations, other criteria may include resistance to opening forces (for use by disabled or infirm) as well as health, safety, durability, risk of vandalism/ligature and aesthetics.

Automatic door closer    
A) Garage-Door Closer.
B) Automatic door closing system 

An automatic door closer (more often called door opener) opens the door itself, typically under the control of a push button, motion detector or other device, and then closes it as well, typically employing a motion or proximity detector to determine when it is safe to close the door.

Leading American manufacturers include Norton, Sargent, Corbin Russwin, and Rixson. Leading European manufacturers include VEL, Briton, Dorma, Geze, Yale and Samuel Heath.

Another type of door closer, a surface mounted one, is attached to the door frame behind the door (where the hinges are) next to the middle hinge. The "arm" rests against the door, and a spring that is bent by the user opening the door closes the door by retracting to its proper shape.

This technology-related article is a stub. You can help Wikipedia by expanding it.